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Accession  No.  (03  5~/  /-       Class  No. 


The  World  of  Matter 


A    GUIDE    TO    THE    STUDY    OF 


CHEMISTRY  AND  MINERALOGY 


BY 


HARLAN   HOGUE   BALLARD,    A.    M. 
\\ 

President  of  the  Agassiz  Association,  Author  of  "Three  Kingdoms," 

"American  Plant  Book,"  "One  Thousand  Blunders  in 

English  Corrected,"  etc. 


LUSTRATED. 


o 


BOSTON,    U.S.A. 

D.    C.    HEATH   &   CO.,    PUBLISHERS 
1894 


•E  ___ 

toBRARV7 


THIS    BOOK 

IS 
AFFECTIONATELY    DEDICATED 

TO 
MY     MOTHER. 


PREFACE. 

In  1875  *he  au*hor  founded  a  society  for  the  study 
of  Natural  Science  at  home,  which,  under  the  name 
AGASSIZ  ASSOCIATION,  has  during  sixteen  years  en- 
listed no  less  than  twenty  thousand  students  of  all  ages, 
and  organized  more  than  one  thousand  local  branch  so- 
cieties scattered  throughout  the  world.  Under  the  aus- 
pices of  the  Agassiz  Association  and  under  the  general 
supervision  of  the  author,  who  has  heretofore  conduc- 
ted the  entire  management  and  correspondence  of  the 
society,  annual  courses  of  experimental  study  have  been 
conducted  by  eminent  teachers,  through  the  mails. 
During  the  present  year  nearly  one  thousand  pupils  in 
the  United  States  are  at  work  on  a  course  in  Mineral- 
ogy under  the  care  of  Professor  Gustave  Guttenberg. 

This  practical  experience  of  sixteen  years  has  firmly 
convinced  the  author  that  the  natural  sciences  are  ordi- 
narily taught  in  a  fragmentary  manner.  Wonderful 
advances  have  indeed  been  made  in  methods  of  teaching 
them  w'thin  twenty  years,  and  there  is  now  a  multitude 
of  competent  and  faithful  teachers,  who,  each  in  his 
own  special  department,  are  training  their  pupils  as 

(3) 


4  PREFACE. 

they  ought  to  be  trained,  discarding  ancient  systems  of 
memorizing  and  rote-work,  and  introducing  laboratory 
and  field-work,  which  develops  and  strengthens  the  natu- 
ral powers  of  perception  and  reason:  but,  rarely,  if 
ever,  has  the  attempt  seriously  been  made  so  to  co-ordi- 
nate the  several  branches  of  science  as  to  cause  the  stu- 
dent to  apprehend  their  essential  unity,  or  even  to  ap- 
proach them  in  a  natural  and  logical  order. 

To  accomplish  this,  is  attempted  in  this  series  of  books. 
A  brief  discussion  of  the  true  order  of  scientific  studies 
is  included  in  Chapter  XIX.,  and  need  not  be  repeated 
here. 

No  one  need  hope  to.  learn  anything  of  much  value 
either  of  chemistry  or  mineralogy  unless  he  handles 
specimens  and  makes  experiments. 

A  collection  of  thirty-six  minerals  has  been  prepared 
to  accompany  this  book.  They  are  arranged  in  a  neat 
case.  They  have  been  selected  under  the.  supervision 
of  Prof.  W.  O.  Crosby,  of  the  Boston  Society  of  Natu- 
ral History,  and  can  be  depended  upon  as  excellent 
typical  specimens,  and  they  are  furnished  at  the  bare 
cost  of  the  labor  required  in  their  preparation.  Never- 
theless it  is  not  necessary  that  the  reader  should  procure 
these  particular  specimens,  as  he  will  be  able  to  find 
similar  ones  almost  anywhere. 

The  author  has  made  free  use  of  the  standard  text- 
books in  Physics,  Chemistry,  and  Mineralogy,  particu- 
larly Ganot,  Roscoe  and  Schorlammer,  Cooke,  Faraday, 
Huxley,  Tenney,  Richards,  Kunz,  and  Dana;  he  is 
especially  indebted  to  the  generous  courtesy  of  the 


PREFACE.  5 

authors  and  Publishers  of  Remsen's  Elements  of 
Chemistry,  Crosby's  Common  Minerals  and  Rocks,  and 
Guttenberg's  Course  in  Mineralogy;  and  he  desires  to 
express  his  gratitude  to  Professors  Ira  Remsen,  W.  O. 
Crosby,  Gustave  Guttenberg,  and  John  B.  Welch,  for 
valuable  suggestions  during  the  progress  of  the  work, 
and  for  reading  the  proofs  while  in  press. 
PITTSFIELD,  MASS.,  September  i5th,  1891. 


CONTENTS. 


CHAPTER.  PAGE- 

PREFACE m- 

I.     A  PIECE  OF  ICE ' 

II.     A  PIECE  OF  ICE  (Continued) 16 

III.  A  GLASS  OF  MELTED  ICE 33 

IV.  Is  WATER  AN  ELEMENT?  .     .     ,     .                    .45 
V.    FIRE 55 

VI.     Am 67 

VII.     EARTH ,     .     .     .  77 

VIII.     QUARTZ 86 

IX.    A  LESSON  IN  CHEMISTRY 94 

X.     A  PIECE  OF  CHARCOAL       „ 103 

XI.     CARBON  CONTINUED 115 

XII.    A  PIECE  OF  MARBLE 126 

XIII.    CLAY                                      137 


CONTENTS. 
CHAPTER.  PAGE. 

XIV.    POTASSIUM— MICA 144 

XV.    A  LUMP  OF  SALT   . 150 

XVI.    MURIATIC  ACID .  156 

XVII.    CHLORINE 161 

XVIII    IRON 165 

XIX.    BY  WAT  OF  REVIEW 171 

XX.    WHAT  is  A  METAL? 179 

XXI.     FAMILIES  OF  ACID-FORMING  ELEMENTS      .     .  184 

XXII.    FAMILIES  OF  METALS 194 

XXIII      How  TO  DETERMINE  MINERALS 198 

XXIV.    FLAME  TESTS,  HEAT  TESTS  AND  ACID  TESTS  .  205 

XXV.    TWELVE  OTHER  MINERALS 216 

XXVI.    BLOW-PIPE  ANALYSIS      ........  226 

XXVII.    SUGGESTIONS  FOR  FURTHER  STUDY   .  245 


THE  WORLD  OF  MATTER. 


CHAPTER  I. 

A    PIECE    OF     ICE. 

Ice  is  one  of  the  most  common  minerals.  Let  us 
begin  our  study  with  a  piece  of  ice.  We  will  not  ask 
any  one  to  tell  us  anything  about  it  until  we  have 
learned  what  we  can  from  our  own  observation. 

Common  sense  is  the  sense  which  we  all  have  in  com- 
mon and  by  the  use  of  our  common  sense,  and  our  common 
senses,  we  can  learn  enough  for  practical  purposes. 
The  senses  which  we  all  have  are  feeling,  sight,  taste, 
hearing,  and  smell.  What  do  these  teach  us  about  a 
piece  of  ice?  We  notice  first  that  it  is  cold,  smooth, 
slippery,  hard,  and  heavy.  We  learn  all  this  from  the 
sense  of  feeling  by  holding  the  piece  of  ice  in  the  hand. 

No  scientist  understands  the  meaning  of  these  words 
better  than  we,  and  no  explanation  can  make  them  any 
plainer.  No  facts  in  natural  science  are  any  more  diffi- 
cult to  understand  than  these.  The  only  reasons  for  the 
popular  notion  that  there  is  something  hard  and  mysteri- 
ous about  chemistry  and  mineralogy  are  that  many  of 
the  substances  treated  of  in  the  books  are  less  familiar  to 
us  than  ice,  and  that  many  of  the  words  used  to  describe 
them  are  new  to  us.  When  a  piece  of  muscovite 

(7) 


8  THE  WORLD  OF  MATTER. 

becomes  as  familiar  to  our  hand  as  a  piece  of  ice,  and 
when  we  become  as  familiar  with  the  words  "transpar- 
ent" and  "foliaceous"  as  we  are  with  the  words  "hard" 
and  "smooth,"  the  statement  that  "Muscovite  is  trans- 
parent and  foliaceous"  will  seem  as  simple  as  that  "Ice  is 
hard  and  smooth." 

This  is  by  the  way,  but  it  is  important,  for  I  wish  the 
reader  to  remember  that  if  he  ever  finds  anything  in  a 
good  scientific  text-book  which  seems  hard  to  under- 
stand, it  will  be  because  he  is  not  familiar  with  the 
thing  described,  or  because  he  does  not  know  the 
meaning  of  the  words  used  to  describe  it,  or  because  he 
has  not  mastered  the  preceding  portion  of  the  book. 

To  remedy  the  first  trouble  it  is  necessary  to  get 
hold  of  the  strange  substance  and  examine  it;  to  remedy 
the  second  trouble  the  strange  words  must  be  clearly 
defined. 

Let  us  return  to  our  piece  of  ice,  and  having  learned 
what  our  hands  can  tell  us  of  it,  let  us  see  what  our 
eyes  can  teach  us.  This  piece  is  thin  and  clear.  It 
looks  like  a  piece  of  glass.  If  we  lay  it  on  this  page 
we  can  read  the  letters  through  it.  If  it  were  large  and 
strong  enough  it  would  do  for  a  window-pane.  The 
light  comes  through  it.  If  we  hold  it  in  the  sunlight  it 
shines  like  glass. 

Testing  it  now  by  our  other  senses  we  find  that  it  has 
no  smell  or  taste,  and  that  when  we  break  it,  it  breaks 
with  a  snapping  or  cracking  sound. 

In  this  connection  we  notice  that  it  is  brittle,  a  fact 
to  which  our  hand,  eye  and  ear  all  bear  witness. 


A   PIECE   OF   ICE.  9 

We  have  spoken  of  our  piece  of  ice  as  a  "thing,"  but 
it  is  better  to  use  the  word  "substance."  This  word  is 
better  because  the  word  "thing"  is  too  indefinite,  being 
used  also  of  events  or  deeds. 

Shall  we  say  then  that  ice  is  a  brittle,  hard,  smooth, 
slippery,  clear,  shining,  heavy,  and  cold  substance, 
without  taste  or  smell?  Not  yet.  All  this  is  true  of 
the  particular  piece  we  are  examining,  but  we  remember 
that  we  have  seen  other  pieces  of  ice  that  were  rough 
instead  of  smooth,  dull  rather  than  shining  and  white 
or  green  instead  of  clear.  We  must  therefore  recollect 
that  we  are  speaking  only  of  a  particular  sample  of 
ice,  not  of  ice  in  general.  Such  a  sample  of  any  sub- 
stance is  called  a  "specimen;"  and  it  is  only  after  a 
study  of  many  specimens,  and  after  rinding  what  is 
true  of  all  of  them,  that  we  shall  be  ready  to  make  a 
general  description  or  definition  of  ice. 

In  all  the  ice  we  have  seen  we  have  observed  cold- 
ness, brittleness,  hardness,  and  weight.  Coldness 
belongs  to  ice  wherever  it  is  found,  and  therefore  is  a 
"property"  of  ice,  as  whatever  belongs  to  a  man  is  his 
property.  Brittleness,  hardness,  and  weight  are  also 
properties  of  ice,  and  as  these  have  all  been  perceived 
through  the  senses,  they  are  called  "physical"  properties. 

The  first  step  in  the  study  of  any  substance  is  the 
determination  of  its  physical  properties. 

A  set  of  mineral  specimens  has  been  prepared  to 
accompany  this  book,  and  in  the  case  of  each  of  them 
you  will  do  well  to  make  a  list  of  its  physical  proper- 
ties as  revealed  by  your  senses,  as  we  have  with  our 


io  THE   WORLD   OF   MATTER. 

piece  of  ice.  The  names  for  such  additional  properties 
as  may  be  observed  will  be  given  and  explained  as  we 
go  on. 

If  you  have  held  your  specimen  of  ice  in  your  hand 
while  examining  it,  you  must  by  this  time  have  observed 
a  remarkable  change  in  it.  It  has  partly  melted.  Its 
edges  are  no  longer  sharp  but  rounded;  it  feels  wet, 
and  water  is  trickling  from  it.  In  a  short  time  there 
will  be  only  a  few  spoonfuls  of  water  instead  of  a  piece 
of  ice.  The  specimen  has  changed  from  a  solid  to  a 
liquid  condition.  This  change  has  been  a  silent  one 
and  has  been  learned  through  the  two  senses,  feeling 
and  sight. 

Up  to  this  point  our  study  has  been  entirely  by 
observation.  We  have  simply  examined  our  specimen 
and  observed  such  of  its  physical  properties  as  have 
revealed  themselves  to  our  senses  without  any  special 
effort  on  our  part.  It  is  now  time  to  go  a  step  further 
and  make  an  experiment.  This  consists  in  placing  our 
specimen  under  new  conditions  and  observing  how  it 
behaves.  If  we  had  placed  the  ice  in  the  hand  with 
the  intention  of  learning  whether  any  effect  would  be 
produced  thereby,  and  if  we  had  then  observed  that  it 
melted,  that  would  have  been  an  experiment.  Experi- 
ments are  made  in  order  to  discover  something  that  we 
cannot  learn  while  our  specimen  remains  under  ordinary 
conditions;  and  they  are  very  frequently  made  in  order 
to  discover  the  cause  of  some  appearance  or  change 
which  we  have  noticed.  Any  such  appearance  or 
change  is  called  in  scientific  language  a  "phenomenon." 


A   PIECE   OF  ICE.  ii 

Whatever  is  perceived  by  any  or  all  the  senses  is  a 
phenomenon.  Among  the  more  common  phenomena 
are  light  and  darkness,  heat  and  cold,  motion  and  rest. 

The  melting  of  ice  is  a  phenomenon,  and  having 
observed  it,  let  us  make  a  few  simple  experiments  in 
order  that  we  may  if  possible  discover  its  cause.  The 
fact  that  in  this  case  we  already  know  the  cause,  is  no 
hindrance  to  the  experiments.  They  will  only  confirm 
us  in  our  present  opinion  if  that  is  right.  First  then 
lay  a  piece  of  ice,  wrapped  in  flannel,  in  a  very  cold 
refrigerator.  This  is  the  experiment.  The  obser- 
vation is  that  it  does  not  melt.  Next  place  it  near  a 
hot  fire.  It  melts.  Try  it  in  hot  and  cold  water.  In 
the  warm  rays  of  the  sun.  Hold  it  in  your  hand  or 
your  mouth.  If  then,  there  is  any  one  condition,  and 
only  one,  which  is  present  in  every  instance  when  the 
ice  melts,  and  always  absent  when  it  does  not  melt,  it 
will  be  reasonable  to  infer  that  whatever  produces  that 
condition  is  the  cause  of  the  phenomenon  of  melting. 
Now,  in  each  experiment  the  condition  of  melting  is 
that  something  warm  be  near  the  ice;  either  warm  air, 
or  a  warm  hand,  or  warm  iron,  or  warm  water;  and  as 
nothing  is  made  warm  without  heat,  we  arrive  at  the 
conclusion  that  heat  causes  ice  to  melt.  This  property 
of  ice,  namely,  that  it  melts  when  heated,  is  termed 
"fusibility."  Ice  is  fusible. 

Our  minds  are  so  constituted  by  nature  that  we 
invariably  look  for  some  cause  for  every  observed 
phenomenon,  and  it  is  a  curious  fact  that  even  before 
we  learn  with  certainty  the  true  cause,  we  can  hardly 


12  THE   WORLD   OF   MATTER. 

refrain  from  risking  a  guess  at  it  as  soon  as  the  phe- 
nomenon is  observed.  It  is  nearly  necessary  to  make 
such  a  guess  before  we  can  undertake  an  intelligent 
experiment,  and  experiments  are  usually  made  with  the 
purpose  of  determining  the  correctness  or  incorrectness 
of  a  previous  guess  at  the  true  cause.  Such  a  guess, 
especially  when  made  the  basis  of  experiments,  is  called 
an  "hypothesis,"  and  hypotheses  are  of  the  highest  value 
in  all  scientific  study. 

An  hypothesis  is  the  first  answer  the  mind  suggests 
to  the  question  "Why?" 

It  must  not  be  confounded  with  a  theory,  which  is  a 
full  and  orderly  explanation  of  a  group  of  observed 
facts  and  phenomena,  and  usually  accounts  for  a  large 
number  of  facts  apparently  different  and  unconnected. 
A  theory  often  rests  on  an  hypothesis;  as  the  Darwinian 
theory  of  the  origin  of  species  depends  largely  upon 
the  hypothesis  that  accidental  variations  may  result  in 
forms  sufficiently  new  and  permanent  to  be  reckoned  as 
distinct  species. 

Having  learned  that  heat  causes  ice  to  melt,  the 
curious  student  will  wish  to  know  what  causes  the  heat; 
and  having  if  possible  discovered  that,  he  will  again 
search  for  the  cause  of  that  cause,  and  so  on  in  an  ever 
lengthening  chain,  until  he  either  reaches  some  first 
cause,  or  becomes  weary  or  discouraged  in  its  pursuit. 
To  this  first  cause  religion  makes  a  short  path  by  assert- 
ing the  existence  of  an  infinite  and  eternal  being,  God, 
Toward  it  science  moves  more  slowly,  following  back 
the  chain  of  effect  and  cause  link  by  link,  and  verifying 


A   PIECE   OF  IC£.  13 

each  conclusion  by  patient  and  prolonged  experiment. 
Some  scientists,  like  Louis  Agassiz,  ultimately  arrive 
at  the  same  theological  conclusion — a  creator,  God; 
others  find  a  first  cause  in  a  universal  and  unintelligent 
force  constantly  acting  under  natural  law;  others 
declare  that  the  first  cause  of  all  natural  phenomena  is 
so  remote  as  to  be  wholly  beyond  the  reach  of  human 
knowledge  or  imagination;  and  others  are  contented  to 
work  as  faithfully  as  may  be  along  the  nearer  and 
clearer  links  in  the  great  chain,  without  speculating 
upon  that  part  of  it  which  is  out  'of  sight.  For  the  present 
we  shall  remain  among  this  latter  class. 

The  question  of  the  nature  and  cause  of  heat  will  be- 
reserved  for  another  chapter. 

Up  to  this  point  our  observations  and  experiments 
nave  been  of  the  simplest  possible  character,  and  have 
consisted  merely  in  observing  those  marked  physical 
properties  of  ice  which  at  once  present  themselves  to 
the  most  careless  mind.  Let  us  now  make  a  somewhat 
more  careful  examination.  Taking  another  specimen 
as  nearly  like  the  one  we  have  melted  as  possible,  we 
not  only  perceive  that  it  is  hard,  but  will  now  raise  the 
additional  question,  "how  hard?" 

In  order  to  test  the  degree  of  hardness  which  any 
mineral  possesses,  it  becomes  necessary  to  have  a  meas- 
ure or  scale  of  hardness.  That  is,  as  in  the  case  of  all 
measuring,  we  must  have  a  known  and  familiar  stand- 
ard with  which  to  compare  each  new  specimen.  The 
scale  adopted  by  mineralogists  consists  of  a  series  of  ten 
specimens,  beginning  with  one  of  the  softest,  talc, 


<4  *THE   WORLD   OF  MATTER. 

whose  hardness  is  called  I,  and  ending  with  the  hardest 
known  mineral  diamond.     The  scale  is  as  follows: 

SCALE  OF  HARDNESS. 

}.  Ta'.o.  6,  Orthoclase. 

2.  Gypsum.  7.  Quartz. 

3.  Calcite.  8.  Topaz  or  beryl. 

4.  Fluorite.  9.  Corundum. 

5.  Apatite.  10.  Diamond. 

Specimens  of  the  first  seven  of  these  are  included  in 
the  collection  which  accompanies  this  book.  They  are 
easily  obtained,  and  as  minerals  harder  than  quartz  are 
very  few  and  very  rare,  they  are  all  that  you  really 
need.  We  test  the  relative  hardness  of  two  minerals  by 
finding  out  which  will  scratch  the  other.  If  any 
mineral,  for  example,  will  make  a  distinct  scratch  upon 
a  piece  of  talc,  it  is  harder  than  talc;  unless,  indeed,  it 
can  itself  be  scratched  as  distinctly  by  a  piece  of  talc,  in 
which  case  they  may  be  considered  to  have  the  same 
degree  of  hardness.  The  reason  that  minerals  of  the 
same  degree  of  hardness  can  scratch  each  other  is 
that  a  sharp  corner  has  a  slight  advantage  over  a 
smooth  surface.  You  can  often  scratch  a  pane  of  glass 
with  a  fragment  broken  from  one  corner  of  it.  ' 

There  is  a  simpler  method  of  testing  the  hardness  of 
minerals,  and  a  method  sufficiently  accurate  after  a  little 
practice.  The  scale  of  hardness  in  this  case  consists  of 
your  thumb-nail,  a  pocket  knife,  and  a  piece  of  ordinary 
window-glass.  Specimens  that  can  be  scratched  with  the 
nail  as  easily  as  talc,  have  a  hardness  expressed  by  the 


A  PIECE  OF  ICE.  i$ 

number  i ;  those  that  offer  more  resistance,  but  yet  can 
be  scratched,  like  gypsum,  have  a  hardness  of  2 ;  those 
that  can  very  easily  be  scratched  with  your  knife-blade 
have  the  3d  degree  of  hardness;  those  that  require  more 
pressure  under  the  blade,  have  hardness  4;  those  that 
can  be  scratched  with  a  knife  with -difficulty,  and  are 
not  yet  hard  enough  to  make  a  scratch  on  glass,  have 
hardness  5;  those  that  make  a  slight  scratch  on  glass, 
and  are  yet  soft  enough  to  be  scratched  by  the  knife- 
blade  with  the  greatest  difficulty,  have  hardness  6;  while 
those  that  easily  scratch  glass  and  resist  the  edge  of  the 
blade,  have  hardness  7  or  more. 

It  must  not  be  considered  a  proof  of  the  softness  of  a 
mineral  that  it  crumbles  under  pressure.  Sandstone 
which  you  can  crush  between  your  fingers  is  often  com- 
posed of  particles  of  quartz  which  will  scratch  glass. 
Test  the  hardness  of  your  specimen  of  ice. 

QUESTIONS  ON  CHAPTER   I. 

1.  What  is  ice? 

2.  Name  four  of  its  physical  properties. 

3.  What  is  a  specimen? 

4.  What  change  takes  place  in  a  piece  of  ice  held  in 
the  hand? 

5.  What  is  the  cause  of  this? 

6.  What  is  the  difference  between  observation  and 
experiment? 

7.  What  is  a  phenomenon? 

8.  What  is  an  hypothesis? 

9.  What  is  a  theory? 

10.     Explain  the  "scale  of  hardness." 


16  THE   WORLD   OF   MATTER. 


CHAPTER  II. 
A  PIECE  OF  ICE — (CONTINUED*) 


At  our  first  examination  of  a  piece  of  ice  we  observed 
that  it  was  heavy.  Let  us  now  determine  how  its 
weight  compares  with  the  weight  of  other  mineral 
specimens  of  the  same  hulk.  This  is  one  of  the  most 
important  points  in  the  study  of  any  specimen.  Here, 
again,  as  in  the  case  of  hardness,  we  must  have  a 
standard  of  comparison;  that  is,  some  substance  with 
whose  weight  we  are  familiar,  with  which  we  may 
compare  each  new  specimen  we  meet.  From  its 
abundance  and  universal  distribution,  water  is  taken  as 
the  standard.  The  weight  of  water  varies,  however^ 
with  its  temperature,  pressure  and  purity,  and  when 
extreme  accuracy  is  required,  we  use  distilled  water, 
weighed  at  a  fixed  temperature — commonly  60  degrees 
Fahrenheit — and  under  such  atmospheric  pressure  as 
raises  the  mercury  in  a  barometer  to  the  height  of  30 
inches:  but  for  our  present  purpose  we  may  neglect 
the  questions  of  temperature  and  pressure,  and  even 
purity,  and  simply  compare  the  weight  or  density  of 
our  specimen  with  that  of  an  equal  bulk  of  whatever 
water  is  most  convenient  to  our  hand.  The  relative 
weight  of  any  substance  as  compared  to  that  of  wate~ 


A   PIECE  OF  ICE.  17 

is  called  its  specific  weight  or  specific  gravity.  If  I 
say  that  the  specific  gravity  of  cast  zinc  is  7,  I  mean 
that  a  piece  of  the  zina  is  seven  times  as  heavy  as  an 
equal  bulk  of  water. 

Students  commonly  find  something  difficult  or  confus- 
ing about  this  term  "specific  gravity,"  because  the  words 
are  unusual.  If  you  do  not  perfectly  understand  it, 
take  one  or  two  more  illustrations.  If  a  cubic  inch  of 
clay  is  twice  as  heavy  as  a  cubic  inch  of  water,  its 
specific  gravity  is  2.  The  specific  gravity  of  melting 
ice  is  .93,  and  this  means  that  a  cubic  inch  or  a  cubic 
foot  of  ice  weighs  -f^35  as  much  as  a  cubic  inch  or  foot 
of  water. 

The  word  "specific"  means  ''belonging  to  a  particular 
kind ;"  so  that  if  we  translate  the  expression  "the  specific 
gravity  of  a  mineral"  into  common  words,  it  reads 
"the  weight  of  a  particular  kind  of  mineral;"  but  we 
must  remember  that  this  does  not  mean  its  absolute 
weight  as  determined  by  the  scales,  but  its  relative 
weight  as  compared  to  an  equal  bulk  of  water. 

The  question  now  arises  how  the  specific  gravity  of 
any  specimen  can  be  determined.  If  our  specimen  hap- 
pened to  be  of  such  a  shape  and  size  as  exactly  to  fit 
into  any  convenient  vessel,  as  a  cup,  it  would  be  a  very 
simple  matter.  We  should  then  fill  the  cup  with  water, 
weigh  it,  and  subtract  the  weight  of  the  empty  cup. 
This  would  give  the  weight  of  the  water.  Then  we 
should  weigh  our  specimen;  and  if  we  found,  for 
example,  that  the  water  weighed  8  ounces,  and  the 
specimen  30,  we  should  know  that  the  specimen  was 


i8  THE   WORLD   OF  MATTER. 

3^  times  as  heavy  as  an  equal  bulk  of  water,  or  that  its 
specific  gravity  was  3.75. 

What  shall  we  do  when,  as  is  nearly  always  the  case, 
our  specimen  is  irregular  in  shape? 

We  might  make  a  mould  in  plaster-of-paris,  which 
would  hold  the  same  bulk  of  water  as  the  specimen, 
and  then  weigh  and  compare  as  before;  but  this  would 
be  tedious,  and  inexact,  particularly  if  our  specimen 
happened  to  be  porous  or  hollow. 

We  might  fill  a  vessel  with  water  quite  up  to  the 
level  of  a  waste-pipe,  as  in  Fig.  i. 


If,  then,  we  lowered  the  specimen  into  the  water  it 
would  displace  an  equal  bulk  of  water  which,  flowing 
out  at  A,  could  be  caught  and  weighed. 

This  also  would  be  a  slow  and  awkward  process,  and 
liable  to  error. 

Just  at  this  point  we  are  greatly  helped  by  a  fact 


A  PIECE  OF  ICE.  19 

which  was  discovered  about  1600  years  ago  by  a 
famous  philosopher  of  Sicily,  named  Archimedes.  The 
interesting  and  amusing  story  of  his  discovery  you  will 
find  in  any  cyclopedia,  but  the  fact  is  this,  that  when 
anything  is  plunged  into  water  it  seems  to  lose  just  as 
much  weight  as  the  weight  of  the  water  it  displaces. 
Now,  of  course,  any  specimen  plunged  into  water  dis- 
places an  amount  of  water  equal  to  its  own  bulk. 
Therefore  if  we  ascertain  how  much  loss  of  weight  a 
specimen  sustains  in  water,  we  know  exactly  how  much 
an  equal  bulk  of  water  weighs.  For  example,  lower  a 
piece  of  zinc  weighing  in  the  air  seven  pounds  into 
water  and  weigh  it  again.  It  now  weighs  only  six 
pounds.  This  means  that  it  has  displaced  exactly  one 
pound  of  water;  or  that  water  equal  in  bulk  to  7  pounds 
of  zinc,  weighs  one  pound ;  or  that  zinc  is  seven  times  as 
heavy  as  water ;  or  that  the  specific  gravity  of 
zinc  is  7. 

To  find  the  specific  gravity  of  any  mineral,  therefore, 
divide  its  weight  in  air  by  its  loss  of  weight  in  water. 
Strictly  speaking,  we  should  use  the  weight  of 
the  specimen  in  a  vacuum  instead  of  in  air,  but 
that  is  not  necessary  for  practical  purposes.  Con- 
venient balances  for  this  air  and  water  weighing  are 
furnished  by  all  dealers  in  chemical  apparatus,  and  need 
not  be  described  here,  particularly  as  you  will  not  need 
to  use  them  until  you  have  advanced  further  in  your 
work.  For  the  present,  after  a  little  practice,  and  a 
careful  handling  of  equal-sized  pieces  of  the  following 
substances,  which  constitute  a  sort  of  specific  gravity 


20  THE   WORLD  OF  MATTER. 

scale  of  approximate  exactness,  you  can  estimate  the 
specific  gravity  of  a  mineral  pretty  closely  by  lifting  it 
in  the  hand. 

SPECIFIC  GRAVITY  SCALE. 

Seasoned  live  oak,  or  ice,  i. 

Gypsum,  or  sulphur,  2.     (Common  feldspar,  2.5.) 

Cryolite,  or  apatite,  3. 

Corundum,  4. 

Magnetite,  or  pyrite,  5. 

Cuprite,  6. 

Cast  zinc,  7* 

Bell  metal,  8. 

Cinnabar,  when  pure,  9.     (Copper  nearly  9.) 

Silver,  10.5. 

Gold,  or  platinum,  20. 

We  have  already  observed  that  ice  shines  in  the  light. 
This  property  is  termed  lustre,  and  the  various  kinds  of 
lustre  are  named  from  substances  in  which  these  varieties 
are  most  commonly  observed;  namely,  glass,  pearl, 
metal,  resin  or  wax,  diamond,  and  silk.  Lustres  resem- 
bling these  are  called  vitreous  or  glassy,  pearly,  metallic, 
resinous  or  waxy,  adamantine,  and  silky.  The  two 
most  important  are  vitreous  and  metallic.  Indeed  a 
chief  division  of  all  minerals  is  into  two  classes; 

i.  Those  that  have  a  metallic  lustre.  2.  Those  that 
have  not.  If  a  mineral  has  no  lustre  at  all  it  is  called 
dull. 

We  observed  that  our  specimen  of  ice  was  clear,  that 
we  could  see  to  read  through  it.  This  property  is  called 


A   PIECE   OF   ICE.  21 

"transparency."  Air,  water  and  glass  are  transparent. 
Minerals  through  which  one  can  perceive  light,  like 
ground  glass  or  smoked  glass,  but  through  which  one 
cannot  distinguish  objects  clearly,  are  said  to  be  trans- 
lucent; those  through  which  no  light  at  all  can  be  seen, 
like  the  metals,  are  called  opaque. 

We  observed  that  our  specimen  was  nearly  colorless, 
yet  we  recollected  that  we  had  seen  ice  that,  instead  of 
being  clear,  was  white  and  green.  This  leads  us  to 
notice  the  distinction  between  the  real,  or  essential  color 
of  a  mineral,  and  its  apparent  color.  The  apparent 
color  of  minerals  is  one  of  their  least  important  proper- 
ties, because  it  arises  from  so  many  different  causes 
that  it  is  very  variable.  This  variability  is  more  marked 
in  transparent  than  in  opaque  substances,  and  often 
arises  from  some  impurity.  Thus  quartz  may  be  white, 
yellow,  red,  green,  blue,  brown,  or  black,  the  color  in 
each  instance  being  due  to  the  presence  of  some  other 
mineral  diffused  throughout  the  quartz.  A  very  minute 
quantity  of  coloring-matter  is  sufficient  to  change  the 
hue  of  a  large  mass,  just  as  a  few  grains  of  indigo  make 
a  large  tank  of  water  blue. 

The  color  of  the  powder  of  any  mineral  is  much  less 
likely  to  be  affected  by  the  presence  of  these  impurities, 
and  we  therefore  regard  that  as  of  far  more  importance 
than  the  apparent  color  in  identifying  it.  This  powder 
may  be  obtained  by  crushing  a  small  fragment,  by 
scratching  the  specimen,  or  by  making  a  mark  with  the 
specimen  upon  a  surface  harder  than  itself.  An 
ordinary  slate-pencil  is  apparently  of  a  dull  lead  color- 


22  THE   WORLD   OF   MATTER. 

but  crush  a  fragment  to  powder,  or  scrape  it  with  a 
knife,  or  observe  the  color  of  the  mark  it  leaves  upon 
the  slate,  and  you  will  learn  that  its  essential  color  is 
light  gray,  approaching  white. 

The  simplest  way  to  observe  this  essential  color,  in 
the  case  of  most  minerals,  as  in  the  case  of  the  slate 
pencil,  is  by  observing  the  color  of  the  mark  or  "streak" 
it  makes  upon  a  harder  surface.  For  this  reason  the 
plate  of  hard  glass  generally  used  to  test  this  color,  is 
called  a  "streak-plate,"  and  the  color  itself  is  called  the 
"streak."  Now  whether  the  apparent  color  of  ice  be 
green  or  blue  or  white,  the  color  of  its  powder  or 
"streak''  is  always  white.  This  is  the  case  also  with 
nearly  all  transparent  and  translucent  minerals,  what- 
ever their  apparent  color  may  be.  The  real  color  of 
ice  appears  most  conspicuously  in  that  form  of  it  known 
as  snow. 

We  have  already  observed  that  ice  is  easily  fusible, 
and  we  have  learned  by  trial  that  the  cause  of  its  melt- 
ing is  heat.  Let  us  now  try  a  further  experiment  with 
a  view  to  determining  the  degree  of  heat  necessary.  To 
test  this  approximately  we  have  only  to  place  the  bulb 
of  a  thermometer  in  a  mixture  of  melting  snow  or  ice, 
and  we  shall  find  that  it  registers  32  degrees  Fahrenheit. 
We  reach  the  same  result  by  placing  the  thermometer 
in  water  which  is  gradually  cooling,  and  reading  it  at  the 
moment  when  freezing  begins,  for  the  freezing-point  and 
the  melting-point  are  so  near  together  as  to  be  practi- 
cally the  same.  It  is  earnestly  hoped  that  the  student 
will  not  be  satisfied  with  reading  about  these  experi- 


A   PIECE    OF   ICE. 


ments,  but  that  he  will  actually  make  them,  no  matter 
how  trivial  they  may  appear.  Otherwise  most  of  the 
advantage  of  this  book  will  be  lost.  Little  facts  are 
constantly  revealing  themselves  to  the  eye  of  the  experi- 
menter of  which  no  mention  is  made  in  the  most 
elaborate  book.  Books  give  general  statements.  They 
record  the  results  of  experiments  made  by  the  most 
skillful  men,  with  the  most  delicate  apparatus,  and 
under  the  most  accurately  defined  conditions. 

Do  not,  therefore,  accept  with- 
out experiment  our  statement  that 
ice  melts  or  water  freezes  at  a 
temperature  of  32  degrees.  Try 
it  with  your  own  thermometer. 
The  chances  are  that  no  ice 
will  appear  on  your  cup  of  water 
until  the  mercury  has  dropped  to 
30  degrees,  perhaps  even  to  28 
degrees  Fahrenheit.  Should  this 
be  the  case  it  would  result  either 
from  the  presence  of  some  im- 
purity, as  salt,  in  the  water,  in- 
crease of  pressure  or  on  account 
of  its  perfect  stillness.  In  the 
latter  case  a  slight  agitation  of  the  water  will  cause  part 
of  it  to  shoot  suddenly  into  crystals  of  ice,  while  the 
temperature  of  the  remainder  will  rise  to  32  degrees. 

A  convenient  apparatus  for  testing  the  freezing-point 
of  water  is  shown  in  Figure  2. 

Snow  sr  pounded  ice  is  placed  in  this  vessel,  from 


Fig.    2. 


24  THE  WORLD  OF  MATTER. 

which  water  escapes  below.  The  bulb  and  part  of  the 
tube  of  a  thermometer  are  immersed  in  this  for  about  a 
quarter  of  an  hour,  and  then  the  mercury  should  stand 
at  32°  j  for  although  the  freezing-point  of  pure  water 
can  be  retarded,  as  has  been  shown,  its  melting  point  is 
always  the  same,  or  at  least  much  less  variable,  as  it 
requires  great  increase  of  pressure  to  lower  it  per- 
ceptibly. In  this  connection  we  mint  notice  two  very 
important  phenomena  which  attend  the  cooling  and 
freezing  of  water,  namely  contraction  and  crystalliza- 
tion. 

EXPERIMENT.      Provide    a    glass    vessel    having    a 
slender  tube  rising  from  a  large  bulb,  as  in  Figure  3. 
Insert  a  thermometer  in  this  vessel.       The 
scale  can  be  read  through  the  glass. 

Fill  the  bulb,  and  half  the  tube  with  water 
and  gradually  heat  it.  If  the  water  rises  in 
the  tube  it  will  show  that  it  is  expanding. 
The  larger  the  bulb  in  proportion  to  the 
stem  the  more  perceptible,  and  apparently 
rapid,  will  be  the  effect.  Now  surround  the 
bulb  with  a  mixture  of  pounded  ice  and  salt 
Fig.  3.  and  note  the  effect  of  cooling  the  water. 
By  all  means  make  this  experiment  yourself,  as  it  forci- 
bly illustrates  the  danger  of  hastily  coining  to  conclu- 
tions  that  may  be  erroneous.  Thus  if  you  perform  this 
experiment  carelessly,  you  will  almost  certainly  decide 
that  water  always  expands  when  heated  and  contracts 
when  chilled.  It  does,  so  far  as  you  have  observed, 
and  you  see  no  reason  why  it  should  ever  act  otherwise. 


A   PIECE   OF   ICE.  25 

But  as  the  water  in  cooling  approaches  the  freezing- 
point  you  must  watch  it  more  attentively.  The  unex- 
pected often  occurs  in  nature.  We' constantly  run  upon 
real  or  apparent  exceptions  to  what  we  have  imagined 
to  be  an  invariable  rule.  The  water  in  the  tube  keeps 
on  contracting  just  as  you  would  expect,  until  it  becomes 
cooled  to  a  temperature  of  about  39°  Fahrenheit,  but 
at  that  point  the  contraction  suddenly  ceases,  and  ex- 
pansion  begins.  The  column  of  cooling  water  in  the 
tube  stops  falling  and  begins  to  rise  again.  This  degree 
of  temperature,  therefore,  39°,  is  the  point  of  the  great- 
est relative  Weight  of  water;  or,  to  speak  scientifically, 
water  at  39°  has  its  maximum  density.  If  you  find  any 
difficulty  in  observing  this  phenomenon  in  the  simple 
tube  just  now  described,  you  can  repeat  an  experi- 
ment first  made  by  Thomas  Charles  Hope,  a  professor 
of  chemistry  in  the  universities  of  Edinburgh  and  Glas- 
gow many  years  ago. 

"Insert  two  thermometers  (Fig.  4,)  at  different  levels 
into  a  cylinder  of  water,  and  chill  the  water  by  apply- 
ing ice  around  the  middle  of  the  vessel.  As  the  water 
becomes  cooled  it  grows  denser,  and  therefore  sinks  to 
the  bottom,  so  that  the  lower  thermometer  falls  until 
it  reaches  39°  Fahr.  Further  cooling  then  expands 
the  water,  instead  of  condensing  it,  and  cqnsequently 
the  cold  water  rises,  so  that  now  the  upper  thermometer, 
which  has  meanwhile  been  almost  stationary,  begins  to 
fall,  and  continues  falling,,  until,  like  the  lower  one,  it 
reaches  39°  Fahr.  The  whole  body  of  water  is  then- 
at  its  maximurri  density,  and  any  further  reduction  of 


26 


THE   WORLD   OF   MATTER. 


temperature  causes  expansion,  the  cold  water  becoming 
specifically  lighter  and  rising  to  the  surface.  Gradually 
the  upper  thermometer  sinks  to  the  freezing  point, 
and  then  a  layer  of  ice  begins  to  form  upon  the  sur- 
face. This  experiment  roughly  imitates  what  occurs 
in  a  natural  piece  of  water,  such  as  a  lake ;  the  surface 
freezes,  while  the  bottom  water  remains  several  de- 
grees warmer." 


Fig.  4 

This  experiment,  while  not  quite  so  simple  as  the 
one  first  described,  has  the  advantage  that  it  makes 
clearer  the  reason  of  the  very  important  fact  that 
water  naturally  freezes  over -first  at  the  top.  Were  it 
not  for  this  strange  property  of  water,  by  virtue  of 
which  it  stops  contracting  and  growing  heavier  just  be- 


A    PIECE   OF   ICE.  27 

fore  it  reaches  the  freezing  point,  northern  lakes  and 
rivers  would  freeze  in  winter  into  solid  masses  of  ice, 
which  would  destroy  all  aquatic  life.  Moreover,  the 
heat  of  summer  would  scarcely  suffice  to  melt  them, 
and  the  climate  might  in  time  be  changed  into  a  per- 
petual winter  such  as  now  lingers  about  the  poles. 

The  increase  in  the  bulk  of  water,  which  begins  at 
39°  Fahr.,  continues  until  the  moment  of  freezing,  when 
a  sudden  and  much  greater  expansion  occurs  with  al- 
most irresistible  force. 

Fill  the  strongest  vessel  you  can  get,  even  a  cannon 
or  hollow  bombshell,  with  water;  plug  it  tight,  and  let 
the  water  freeze:  you  will  have  ample  evidence  of  this 
force. 

Do  not  now  jump  to  the  conclusion  that  all  liquids 
behave  in  the  same  way  as  water  under  like  conditions, 
and  do  not  consult  books  in  order  to  find  out,  but  if  you 
care  to  know,  test  them  carefully  yourself,  one  by  one. 

One  experiment  devised  and  performed  by  yourself 
may  be  of  more  educational  value  than  a  year's  study  of 
text-books. 

The  ice  which  forms  upon  water  appears  at  first  sight 
to  be  a  solid  mass  without  definite  structure.  It  is  really, 
however,  built  up  of  innumerable  crystals,  each  of  a 
definite  shape,  which  are  so  interlocked  and  compacted 
together  that  their  separate  forms  are  obscured.  Pro- 
fessor Tyndall  succeeded  some  -years  ago  in  revealing 
this  hidden  architecture,  by  sending  a  beam  of  sunlight 
through  a  block  of  ice.  Enough  heat  penetrates  the  ice 
from  such  a  ^unbeam  to  cause  a  slow  melting  inside  the 


28  THE   WORLD    OF   MATTER. 

block.  This  first  manifests  itself  by  the  appearance  of 
little  glistening  points,  and  then  rays  of  light  shoot  out 
from  these  bright  centres  until  the  ice  seems  full  of 
shining  snowflakes.  These  beautiful  forms  have  been 
called  "ice-flowers."  They  are  not  really  ice-crystals, 
however,  but  only  the  moulds  left  by  the  melted 
crystals,  and  now  nearly  filled  with  water,  which  re- 
flects the  light  and  discloses  the  secret  of  the  structure 
of  the  ice.  The  glistening  point  in  the  centre  of  each 
liquid  star  is  a  vacuum  or  empty  space  left  by  the  water 
which  shrinks  as  it  melts;  and  the  surface  of  water  as  it 
curves  about  this  vacuum  shines  in  the  sun  like  silver. 

The  beauty  and  symmetry  of  ice-crystals,  which  the 
solid  ice  kept  for  ages  locked  up  in  its  frozen  breast  un- 
til Professor  Tyndall  opened  it  with  his  key  of  light,  is 
nevertheless  plainly  shown  to  us  in  every  shower  of 
snow;  when,  if  the  air  is  still,  each  flake  that  falls  is  a 
perfect  and  exquisite  crystal.  You  will  be  well  repaid 
for  your  pains  if  you  catch  a  number  of  these  snow- 
crystals  next  winter  upon  a  cold  pane  of  glass,  or  a  black 
cloth,  and  study  them  with  a  microscope.  The  variety 
of  forms  which  they  assume  is  infinite,  and  their  beauty 
indescribable;  yet  it  will  be  found  that  they  are  all 
fashioned  on  a  definite  plan,  and  have  their  delicate 
rays  always  arranged  in  threes  or  sixes.  These  six- 
angled  or  hexagonal  flakes,  however,  are  not  regarded 
as  single  ice-crystals,  but  rather  as  many  little  crystals 
symmetrically  united.  I  have  never  been  able  to  see 
satisfactorily  and  clearly  one  of  the  tiny  crystals  of  which 
these  snow-stars  are  saicl  to  be  composed,  but  the  "books" 


A   PIECE   OF  ICE. 


Fig.  6. 


say  that  their  form  is  that  shown  in  Fig.  6;  that  is  to 
say,  a  solid  bounded  by  six  equal  Iczenge- 
shaped  surfaces.  These  diamond  -shaped  sur  - 
faces  are  called  "rhombs,"  by  the  geometri- 
cians, and  asolid  of  the  form  shown  in  Fig.  6  is 
called  a  "rhombohedron."  Just  how  these 
tiny  rhombohedrons  are  joined  together  or 
modified  to  produce  the  six-angled  or  "hex- 
agonal" forms  seen  in  snow-flakes  and  "ice- 
flowers"  can  not  be  clearly  understood  until  you  get 
glass  or  wooden  models  and  experiment  with  them. 
If  you  have  a  model  of  a  rhombohedron,  you  will  see 
that  you  can  hold  it  so  that  an  end  view  presents  a  six- 
sided  outline;  just  such  a  form,  in  fact,  as  appears  in  the 
centre  of  a  snow-flake.  Now  as  these  snow-flakes  are 
usually  transparent,  always  very  thin  and  delicate,  and 
as  it  is  difficult  to  examine  them  with  a  glass  of  high 
magnifying  power,,  it  is  not  impossible  that,  instead  of 
being  flat,  hexagonal  prisms,  as  they  are  commonly 
supposed  to  be,  they  are  really  rhombohedrons,  whose 
upper  edges  escape  our  observation ;  and  it  may  afford  you 
some  interest  to  examine  them  for 
yourself  next  winter. 

In  one  of  the  snow-crystals  drawn 
at  Greenwich,  England,  by  Mr. 
Glaisher,  and  printed  in  Tyndall's 
"  Forms  of  Water,"  the  rhombo- 
hedral  form  of  ice  is  clearly  shown 
in  the  six  crystals  which  surround 
hexagonal  centre,  Fig.  7,  and  if  we  may  suppose 


36  THE  WORLD  OF  MATTED. 

Mr.  Glaisher  to  have  overlooked  the  delicate  angles 
of  the  central  portion  of  this  snow- 
flake,  which  would  only  be  revealed 
by  the  closest  observation,  we  may 
supply  them,  as  in  Fig.  8;  and  then 
we  have  a  compound  crystal,  sym- 
metrically composed  of  regular 
rhombohedrons,  instead  of  a  com- 
bination of  rhombohedrons  with  a 
central  hexagonal  prism.  F'g  8- 

When  a  very  thin  film  of  water  freezes  on  a  smooth 
surface,  as  the  moisture  on  a  window-pane,  its  crystals 
do  'not  usually  present  to  the  eye  either  the  hexagonal 
or  rhombohedral  form  assumed  by  vapor  that  freezes  in 
the  air  and  falls  as  snow.  They  curve  in  marvellous 
imitations  of  trees  and  flowers;  they  build  themselves 
into  fairy  castles  with  crystal  towers  and  battlements; 
they  shoot  into  twinkling  spears  and  glistening  needles; 
they  curl  into  waving  plumes  of  exquisite  grace  and 
beauty.  It  is  fascinating  to  make  photographs  of  this 
frost-work.  It  is  not  impossible  that  by  a  comparison 
and  study  of  a  large  number  of  such  photographs  we 
might  learn  the  secret  of  the  curves  and  angles  that 
seem  so  capricious  in  their  loveliness.  Do  the  shooting 
crystals  follow  the  curve  of  some  eddying  current  of 
air?  Do  they  run  along  some  slight  irregularity  in  the 
structure  of  the  glass?  Are  they  modified  by  the  near- 
ne£s  of  nails  or  other  forms  of  metal?  Are  they  con- 
trolled at  all  by  musical  tones?  Can  they  be  affected  by 
a  gentle  current  of  electricity?  Here  is  an  enticing  field 
for  observation  and  experiment. 


A    PIECE   OF  ICE.  31 

A  kind  of  ice-crystal  less  commonly  noted  occurs  in 
moist  ground,  in  the  shape  of  long  sharp  blades  and 
needles  projecting  an  inch  or  more  from  the  surface  of  the 
ground,  and  standing  like  elfin  troops  on  drill,  all  armed 
with  gleaming  bayonets.  Along  the  margins  of  brooks 
in  winter  are  found  still  more  wonderful  forms  of  crystal 
architecture.  Drooping  ferns  and  curling  leaves  and 
waving  blades  of  grass  are  reproduced  along  the  edge 
of  the  shivering  water,  giving  one  the  impression  that 
the  plants  that  fringed  the  stream  in  summer  are  reap- 
pearing in  shadowy  shapes  of  ice. 

One  December  evening  there  came  a  chilling  fog. 
Later  the  mercury  fell  rapidly,  and  a  rush  of  cold  fol- 
lowed, as  if  a  window  had  been  opened  into  the  Arctic 
zone.  In  the  morning  the  fog  was  gone,  the  sun  shone 
bright,  and  the  sky  was  blue;  but  every  strip  of  exposed 
metal,  and  every  edge  of  unpainted  wood,  was  bordered 
by  a  fringe  of  soft  white  feathers  ranged  as  closely 
together  as  the  down  on  the  breast  of  an  eider-duck. 
On  our  front  porch  is  a  wire  netting  for  summer 
vines  to  run  on,  consisting  of  hexagonal  meshes  two 
inches  in  diameter.  Never  clematis  or  ivy  decked  this 
slender  trellis  so  gracefully  as  the  vine  of  water-crystals 
on  tnat  icy  morning.  The  sudden  and  unwonted  beauty 
brought  exclamations  of  delight  to  the  lips  of  all  who 
saw  it;  but  before  a  camera  could  be  found  to  preserve 
the  picture,  the  sun  silently  undid  the  fastenings  of  the 
tiny  plumes,  and  they  dropped  to  the  earth  in  showers 
of  silvery  sheen. 


32  THE  WORLD  OP  MATTER. 

QUESTIONS    ON    CHAPTEIl    1. 

1.  What  is  the  specific  gravity  of  a  mineral? 

2.  How  is  it  determined  ? 

3-  A  piece  of  lead,  whose  specific  gravity  is  n.4» 
weighs  in  the  air,  456  grains; -what  is  the 
weight  of  an  equal  bulk  of  water? 

4.  How  much  does  this  same  piece  of  lead  weigh  in 

water? 

5.  A  piece  of  glass  Weighs  in  air    24   ounces;    in 

water  16  ounces:  what  is  its  specific  gravity?. 

6.  What  is  "vitreous  lustre?'* 

7.  What  is  the  «' streak"  of  a  mineral? 

8.  What  is  the  melting-point  of  ice? 

9.  Describe  the  expansion  and  contraction  of  water. 

10.  At  what  temperature  does  water  reach  its  maxi- 

mum density? 

1 1.  Describe  an  experiment  to  prove  this. 

12.  Explain  the  structure  of  ice. 


A  GLASS   OF  MELTED   ICE. 


CHAPTER  III. 

A  GLASS  OF  MELTED  ICE. 

Is  water  melted  ice — or  is  ice  frozen  water?  In  one 
sense  both  statements  are  true,  but  the  latter  is  the 
popular  form,  while  the  former  is  the  more  accurate 
and  scientific.  It  is  more  accurate  because  ice  is  the 
natural  or  normal  form  of  this  mineral  when  left  to 
itself,  and  it  is  only  by  the  application  of  heat  that  it  is 
forced  into  the  form  of  water  and  kept  in  that  form;  it 
is  more  scientific  also  because  it  agrees  better  with  our 
way  of  thinking  of  other  mineral  substances,  the  great 
majority  of  which  are  most  familiar  to  us  in  their  "ice," 
or  frozen,  or  solid  state.  Thus  when  we  speak  of  iron, 
lead,  copper,  or  sulphur,  we  naturally  think  of  the 
solid  metal  or  stone,  and  when  these  substances  are 
melted  we  do  not  give  them  new  names  as  in  the  case 
of  ice  and  water  but  speak  of  them  as  melted  iron, 
melted  sulphur,  etc.  At  all  events  there  is  a  gain  for 
our  present  purpose  in  thinking  and  speaking  of  the 
mineral  which  we  are  studying  as  ice,  and  in  regarding 
what  is  usually  called  a  glass  of  water  as  a  glass  of 
melted  ice.  There  may  be  people  living  in  the  frigid 
zone  to  whom  this  matter  of  thinking  has  always 
appeared  the  natural,  perhaps  the  only  one. 

We  are  now  ready  for  a  simple  experiment  with  a 
glass  of  melted  ice. 

3 


34  THE   WORLD   OF   MATTER. 

Hold  a  lump  of  sugar  so  that  one  corner  of  it  dips 
into  the  melted  ice,  and  first  observe  the  sugar.  It 
will  be  seen  that,  beginning  at  the  bottom  it  rapidly 
changes  from  white  to  transparent  gray,  and  that  it  is 
growing  wet  and  beginning  to  soften  and  dissolve.  It 
seems  to  absorb  the  water  like  a  sponge,  and  in  a  short 
time  is  evidently  soaked  through.  This  rise  of  the 
liquid  into  and  through  the  sugar  is  explained  in  the 
same  way  as  the  rise  of  oil  in  a  lamp-wick,  or  through 
any  very  small  tube;  that- is  to  say,  as  due  to  the  draw- 
ing power  of  the  sides  of  the  minute  openings  through 
which  the  liquid  rises,  added  to  the  drawing  power  or 
attraction  of  the  particles  of  liquid  for  one  another. 
The  attraction  between  the  solid  and  liquid  is  called 
adhesion^  because  the  liquid  adheres  to  the  solid ;  the 
attraction  between  the  particles  of  the  liquid  is  called 
cohesion,  because  the  particles  cohere  to  one  another. 
The  walls  of  the  tubes  or  pores  which  contain  the 
liquid  attract  those  liquid  particles  which  are  nearest 
them  and  thus  cause  a  thin  film  of  the  liquid  to  spread 
out  and  upward  on  their  surfaces.  As  this  film  of  the 
liquid  is  forced  upward  it  draws  with  it  the  whole 
column  of  liquid,  and  this  continues  up  to  the  point 
when  the  weight  of  the  rising  column  equals  the 
attractive  force.  From  this  it  will  be  seen  that 
this  attraction  is  not  a  new  force,  but  simply  the  united 
action  of  the  ordinary  forces  of  adhesion  and  cohesion; 
and  it  is  also  evident  that  the  elevation  of  the  liquid 
will  be  greatest  in  the  smallest  tubes,  since  the  weight 
of  the  column  to  be  raised  is  there  least  in  proportion 


A  GLASS   OF  MELTED   ICE.  ~  34 

to  the  amount  of  liquid  which  comes  in  contact  with 
the  walls  of  the  tube.  This  explanation  was  first  given 
by  Leslie  in  1802.  The  Latin  word  for  hair  is  capillus, 
and  since  the  phenomenon  I  have  been  describing  is 
best  observed  in  very  small,  hair-like  or  "capillary" 
tubes,  this  form  of  force  is  called  "capillary  attrac- 
tion." 

Let  us  now  repeat  the  experiment — this  time,  how- 
ever, turning  our  attention  to  the  melted  ice  under  the 
sugar.  As  soon  as  the  sugar  touches  the  liquid  fine 
wavy  and  syrup-like  streams  are  seen  to  flow  from  it 
down  into  the  glass,  where  they  presently  grow  thinner 
and  disappear.  This  continues  until  the  last  particle  of 
sugar  crumbles  in  the  hand  and  loses  itself  in  the  liquid 
below.  The  sugar  is  now  said  to  be  dissolved.  Sub- 
stances which  can  be  dissolved  are  called  "soluble,"  and 
the  liquid  which  has  the  power  of  dissolving  them  is 
called  a  "solvent." 

Find  by  experiment  as  many  different  substances  as 
you  can  that  dissolve  in  water,  and  ascertain  whether 
heating  the  water  renders  their  solution  more  or  less 
easy  and  rapid.  In  connection  with  these  experiments 
test  the  temperature  of  the  water  before  and  after  the 
addition  of  the  substance  to  be  dissolved. 

Make  a  strong  solution  of  alum  and  allow  the  water 
to  evaporate  slowly.  It  wilj  be  observed  that  a  portion 
of  the  alum  is  deposited  from  the  solution  in  the  form 
of  crystals;  and  the  important  fact  is  learned  that 
crystallization  occurs  not  only  on  the  solidification  of 
minerals  by  freezing — as  in  the  case  of  ice — but  that  it 


36  THE  WORLD  OF  MATTER. 

also  usually  accompanies  the  solidification  of  a  dis- 
solved mineral  on  the  evaporation  of  its  solvent. 

Professor  Tyler  suggests  the  following  interesting 
experiments.  Make  a  strong  solution  of  blue  vitriol, 
Which  is  a  compound  of  sulphuric  acid  and  copper. 
Put  this  in  a  warm  place  and  suspend  a  pebble  or  cinder 
in  it.  Notice  the  form  and  color  of  the  crystals  which 
form  upon  the  pebble.  Now  mix  equal  parts  of  alum 
and  blue  vitriol,  make  a  strong  solution  of  the  mixture 
and  allow  the  water  to  evaporate.  The  resulting 
crystals  are  most  interesting.  There  is  a  mixture  of 
the  two  solids,  but  the  crystals  of  the  alum  are  distinct 
from  those  of  the  vitriol,  and  with  care  you  can  almost 
completely  separate  the  blue  crystals  from  the  white. 
Thus  the  minute  particles  which  have  been  held  in 
solution  not  only  combine  in  crystal  form,  but  particles 
of  the  same  substance  unite  in  crystallization  with  one 
another,  and  not  with  those  of  another  substance  even 
when  mingled  in  the  same  solution. 

It  appears  also  from  this  experiment,  that  solids  in 
solution  do  not  necessarily  unite  with  particles  of  their 
solvent  so  as  to  form  a  new  and  distinct  substance,  but 
that  they  may  be  merely  mixed  with  those  particles, 
though  in  so  finely  divided  a  state  as  to  be  indistinguish- 
able to  the  eye. 

Water  has  been  called  -the  "universal  solvent,"  not 
only  because  of  its  universal  distribution,  but  because 
it  dissolves  a  larger  number  of  substances,  both  solid 
liquid,  and  gaseous,  than  any  other  mineral. 

This  solvent  power  of   water  is  one  of   its  most  val- 


A  GLASS  OF  MELTED  ICE.  37 

uable  properties.  On  it  depend  many  of  the  phenom- 
ena of  nature,  and  many  of  the  processes  of  art  and 
manufacture.  The  substances  that  dissolve  in  water 
are  so  numerous,  and  so  universally  distributed,  that 
it  is  doubtful  whether  a  single  gallon  of  chemically 
pure  water  could  be  collected  in  the  whole  world  from 
natural  sources.  Of  these  soluble  substances  salt  is 
one  of  the  most  abundant,  and  countless  rivers  are  con- 
stantly carrying  one  or  both  of  its  elements  to  the  sea. 

Professor  Tyler  says,  that  although  the  proportion 
of  dissolved  matter  in  the  ocean  is  not  large,  yet  it  is 
always  growing  greater,  and  it  has  been  estimated  that 
there  is  now  enough  in  the  whole  ocean,  if  it  could  be 
separated,  to  form  a  mountain  range  larger  than  the 
Alps. 

The  water  that  issues  from  springs  and  wells  is  usually 
"hard;"  that  is,  impregnated  with  lime  or  some  other 
mineral  in  solution,  which  decomposes  soap,  and  thus 
renders  the  water  unfit  for  washing.  Even  rain-water, 
which  is  the  purest  form  in  nature,  is  tainted  with  im- 
purities, caught  and  dissolved  by  the  water  as  it  falls 
through  the  air. 

To  this  property  of  water  we  owe  all  our  mineral 
springs;  to  it  we  must  refer  our  deposits  of  iron  ore. 
It  is  the  cause  of  the  formation  of  great  caves  in  the 
earth  with  their  wonderful  and  exquisite  stalactites 
and  stalagmites ;  it  is  even  largely  responsible  for  the 
valleys  between  the  mountains,  and  for  much  of  the 
scenery  of  the  world,  which  it  reduces  to  forms,  smiling 
and  peaceful,  or  frowning,  abrupt,  and  grand.  With 


38  THE   WORLD   OF   MATTER. 

out  it  the  vegetable  world  could  not  draw  its  support 
from  the  earth,  the  blood  could  not  circulate  in  the  veins 
of  animals,  and  all  life  would  perish  from  the  earth. 
Do  not  pass  this  subject  hastily.  Think  about  it.  Make 
a  list  of  as  many  other  advantages  and  disadvantages 
that  arise  from  the  solvent  power  of  water  as  you  can. 

Do  not  forget  its  cleansing  power  on  the  one  hand, 
nor  on  the  other  the  dangers  that  arise  from  its  power 
of  dissolving  poisonous  or  putrefying  substances. 

In  connection  with  this  last  suggestion,  consider  the 
wisdom  of  removing  as  far  as  possible  from  your  water- 
supply  every  thing  that  is  unclean  or  unwholesome. 
Typhoid  fever  and  many  other  dread  diseases  result 
from  drinking  water  which  holds  in  solution  or  in  sus- 
pension the  invisible  but  certain  seeds  of  death. 

Owing  to  the  selective  power  of  the  crystallizing  par- 
ticles of  any  mineral,  by  virtue  of  which  they  unite 
only  with  others  of  the  same  sort,  as  already  shown  in 
the  case  of  alum  and  blue  vitriol,  ice  freely  formed 
upon  a  lake  is  more  free  from  impurities  than  the 
water  under  it.  There  is  a  truth  in  the  popular  saying, 
that  the  "dirt  freezes  out."  Yet  it  is  a  dangerous  error 
to  suppose  that  all  ice  is  pure,  and  safe  for  domestic 
use.  If  dirty  water  freezes  solid,  all  the  impurities  con- 
tained in  the  water  will  be  retained  in  the  ice.  They 
do  not  unite  in  crystallization  with  the  particles  of  ice, 
but  they  are  caught,  and  held  in  the  ice,  just  as  a  stick 
would  be  if  plunged  in  freezing  water;  and  when  the 
ice  is  melted  they  are  again  set  free,  and  the  freezing 
does  not  destroy  their  unwholesome  and  dangerous 


A   GLASS   OF  MELTED   ICE. 


39 


properties.  Even  when  only  the  surface  of  foul  water 
freezes,  these  impurities  are  but  partially  expelled,  so 
that  it  is  a  safe  rule'that  dirty  water  makes  dirty  ice, 
and  deadly  water  makes  deadly  ice. 

Let  us  now  return  to  our  glass  of  melted  ice.  You 
remember  that  this  was  produced  from  a  transparent 
solid  by  the  action  of  heat,  and  that  it  is  kept  in  its 
present  liquid  form  by  the  continued  action  of  the  same 
force.  We  will  now  make  the  experiment  of  apply- 
ing a  greater  amount  of 
heat  to  the  melted  ice. 

Pour  the  water  into  a 
glass  flask,  or  a  tin  cup, 
put  a  thermometer  in  it, 
and  place  it  over  a  spirit- 
lamp, or  gas-jet,  or  set  it  on 
a  stove.  Fig.  9.  At  first 
no  change  is  observed,  ex- 
cept that  by  close  obser- 
vation you  may  see  that 
the  liquid  is  expanding; 
but  as  the  temperature 
approaches  212  degrees 
Fahrenheit,  bubbles  ap- 
pear on  the  bottom  and 
sides  of  the  vessel  where 
it  is  hottest.  These  first 
bubbles  are  due  to  the  separation  of  particles  of  air 
which  have  been  previously  dissolved  or  absorbed  by 
the  water.  A  little  later,  small  bubbles  begin  to  come 


40  THE  WORLD  OF  MATTER. 

from  the  heated  portion  of  the  water,  and  as  they  rise 
through  the  cooler  liquid  above  they  disappear.  The 
formation  and  disappearance  of  these  bubbles  is  accom- 
panied by  a  peculiar  "singing"  sound.  After  this,  larger 
bubbles  rise  and  burst  on  the  surface,  and  little  clouds 
of  vapor  begin  to  appear,  while  the  whole  mass  of  water 
is  agitated.  The  thermometer  now  stands  at  212 
degrees  Fahrenheit.  This  phenomenon  is  called  boil- 
ing, or,  in  scientific  phrase,  ebullition. 

As  this  boiling  continues,  the  water  is  observed  to  be 
growing  rapidly  less  in  quantity,  and  after  a  short  time 
wholly  disappears.  The  thermometer  meanwhile  has 
remained  stationary  at  212  degrees.  Now,  nothing  has 
been  seen  to  pass  from  your  flask  except  the  vaporous 
clouds  already  mentioned,  and  it  thus  becomes  evident 
that  unless  some  other  way  can  be  discovered  to  account 
both  for  the  disappearance  of  the  water,  and  also  for 
the  appearance  of  the  vapor,  we  must  conclude  that  the 
water  has  been  changed  into  the  vapor,  and  has  passed 
out  of  the  vessel  in  that  form. 

It  is  astonishing  that  so  large  a  quantity  of  water  can 
so  rapidly  escape  in  so  air}-  and  intangible  a  form;  and 
the  vapor  itself  has  so  completely  disappeared  in  the 
air  that  we  find  it  hard  to  believe  that  the  water  which 
has  been  "boiled  away"  has  not  actually  been  destroyed. 
If  not,  where  is  it?  In  order  to  settle  this  point,  we 
must  devise  some  method  of  catching,  and  examining 
the  vapor,  instead  of  allowing  it  to  escape. 

Hold  a  cold  glass  jar,  mouth  down,  over  the  neck  of 
{he  flask,  ^s  it  rjecornes  filled  with  vapor  you  will 


A   GLASS   OF  MELTED   ICE.  41 

observe  that  its  sides  grow  foggy,  and  presently  drops 
of  water  appear,  and  begin  to  trickle  down  inside. 

Is  it  not  plain  that  the  vapor  is  only  another  form  of 
water,  forced  into  this  condition,  and  kept  there  by 
heat?  So  much  of  this  heat  now  leaves  the  vapor  and 
is  expended  in  warming  the  cold  sides  of  the  jar,  that 
there  is  not  enough  left  to  hold  the  water  in  its  vapor- 
ous form,  and  it  again  becomes  liquid,  and  re-appears 
in  the  form  of  water.  This  return  of  vapor  to  the  liquid 
form  on  the  withdrawal  of  heat  is  called  condensation. 
The  process  of  boiling  a  liquid  to  transform  it  into 
vapor,  and  then  cooling  the  vapor  and  collecting  again 
the  condensing  liquid,  is  called  distillation,  and  as  the 
liquid  on  vaporizing  leaves  most  of  its  impurities  be- 
hind, this  is  the  simplest  and  best  method  of  obtaining 
most  liquids,  and  water  among  them,  in  the  purest  pos- 
sible condition. 

You  may  wonder  why  I  have  not  called  this  water- 
vapor  steam.  It  is  not  steam  in  the  strict  sense.  Steam 
is  invisible.  If  you  look  at  the  neck  of  your  flask 
while  the  water  is  briskly  boiling  in  it,  you  will  see 
no  appearance  of  vapor,  and  the  flask  above  the  water 
appears  quite  empty;  yet  it  is  really  filled  with  steam. 
On  leaving  the  mouth  of  the  flask  this  steam  becomes 
partially  condensed  in  the  air,  and  then  appears  in 
vaporous  clouds.  Indeed,  I  have  here  used  the  word 
"vapor"  in  the  popular  rather  than  the  scientific  sense. 
Strictly  speaking,  the  invisible  steam  is  the  true  vapor, 
and  the  white  cloud  is  composed  of  minute  particles  oi 
water  condensed  from  the  vapor. 


42  THE   WORLD   OF  MATTER. 

Another  phenomenon  presented  by  water  bears  a  close 
resemblance  to  the  production  of  steam  by  boiling,  yet 
with  important  differences. 

From  all  exposed  surfaces  of  water  there  is  a  constant 
and  usually  unnoticed  passage  of  a  portion  of  the  water 
into  the  form  of  vapor.  This  is  called  evaporation. 
It  differs  from  boiling  in  two  respects,  first,  it  takes 
place  only  at  the  surface,  and  slowly ;  while  boiling 
produces  steam  throughout  the  mass  of  the  liquid,  and 
rapidly;  second,  it  occurs  at  no  fixed  temperature; 
while  boiling,  as  we  have  seen,  occurs,  under  ordinary 
pressure,  only  at  212  degrees  Fahrenheit.  Vapor  is 
formed  directly,  even  from  ice,  without  intermediate 
melting.  Ice  "wastes  away,"  even  in  cold  weather; 
and  our  laundry. women  are  right  in  saying  that  clothes 
hung  out  in  winter  "freeze  dry."  It  would  take  many 
volumes  to  trace  the  results  of  boiling  and  evaporation. 
Modern  civilization  depends  largely  upon  steam,  which 
not  only  cooks  much  of  our  food,  but  furnishes  most 
of  our  power.  It  would  seem  as  if  the  old  Arabian 
tales  of  Aladdin's  lamp,  and  the  Fisherman  and  the 
Genie,  were  intended  as  parables  to  illustrate  the 
wonders  of  steam.  Aladdin  rubs  his  lamp,  the  emblem 
of  fire,  and  the  strange  fire-spirit  appears,  ready  to  do 
his  bidding.  From  the  Fisherman's  casket  arises  a 
huge  mass  of  vapor,  which  gradually  assumes  the  form 
of  a  puissant  being  capable  of  any  act  of  helpful  min- 
istration or  mad  destruction. 

To-day  with  our  lamp  we  have  evoked  a  spirit  no 
less  powerful;  capable  like  the  Genie  of  expanding 


A  GLASS  OF  MELTED  ICE.  43 

until  the  sky  seems  full,  and  of  contracting  to  the  limits 
of  an  iron  pot;  when  under  due  control,  it  drives  our 
locomotives  across  the  continent,  runs  our  looms  and 
spindles,  heats  our  homes  and  lights  our  streets;  if  un- 
controlled, it  tears  our  engines  to  pieces,  wrecks  our 
habitations,  and  destroys  our  lives.  Like  electricity, 
magnetism,  and  the  explosive  force  of  powder,  steam 
is  one  of  the  invisible  but  mighty  brotherhood  of  fire- 
spirits,  and  repeats  to-day  to  all  who  know  how  to  keep 
it  in  control,  the  formula  used  by  the  obsequious  Genie 
of  old,  "I,  and  the  others,  slaves  of  the  lamp!" 

From  every  rivulet  and  river,  from  every  lake  and 
sea,  from  the  whole  expanse  of  ocean,  vapor  is  con- 
stantly rising,  invisibly  or  in  fantastic  wreaths  of  mist; 
and  this  collects  in  spreading  clouds  which  fill  the  sky, 
cover  the  world  with  cooling  shade,  and  gently  fall  in 
showers  that  refresh  the  thirsty  earth,  bringing  life  to 
every  herb  and  tree,  to  animals  and  man;  or  else,  uniting 
in  hostile  fury,  they  sweep  over  the  earth  in  a  cyclone ; 
then  "heavily  they  fall  on  the  sea,  and  from  its  very 
bottom  crash  down  the  whole  expanse." 

QUESTIONS    ON    CHAPTER    3. 

1.  What  keeps  water  in  its  liquid  form? 

2.  Give  an  illustration  and  an    explanation  of  "capil- 
lary attraction.'' 

3.  How  is  the  temperature  of  water  affected  when 
salt  is  dissolved  in  it? 

4.  Why  is  water  called  the  "universal  solvent?" 


44  THE  WORLD  OF  MATTER. 

5.  What  important  results  follow  this  solvent  action 
of  water? 

6.  Does  foul  water  "freeze  clean?" 

7.  Describe  the  process  of  ebullition. 

8.  At  what  temperature  does  water  boil? 

9.  Distinguish  between  steam  and  other  vapor. 
10.  Describe  and  explain  "condensation." 


WATER  AN  ELEMENT?  45 


CHAPTER  IV. 

IS  WATER  AN  ELEMENT? 

From  the  experiments  and  observations  outlined  in 
the  preceding  chapters,  we  have  learned  that  water 
exists  in  three  different  forms  or  "states,"  namely,  as 
a  solid,  a  liquid,  and  a  vapor,  or  gas.  It  has  also  been 
learned  that  these  forms  follow  one  another  in  the 
order  given  upon  the  addition  of  heat,  and  that  upon 
the  gradual  removal  of  the  heat  the  steam  again 
condenses  into  water,  and  the  water  crystallizes  into 
ice. 

Whether  other  minerals  under  like  conditions  pass 
through  these  same  three  states  must  be  left  for  your 
future  experiments  to  decide;  though  you  know  by 
former  experience  that  different  substances,  such  as 
lead,  iron,  sulphur,  and  wax  may  exist  both  in  the 
solid  and  liquid  form ;  and  you  know  that  others,  as 
alcohol,  naptha,  petroleum,  and  ether,  are  easily 
changed  from  liquids  to  gases. 

Consider  that  expression  "different  substances."  Are 
ice  and  water  and  steam  three  different  substances? 
We  have  seen  that  they  are  only  three  different  forms 
of  the  same  substance;  and  a  proof  is  that  one  can  be 
converted  into  the  other  at  will. 

Suppose,  now,  in  the  first  of  three  cups  you  have  a 
quantity  of  leaden  bullets,  in  the  second  a  number  of 


46  THE   WORLD   OF  MATTER. 

iron  balls,  arid  in  the  third  a  mixture  of  iron  balls  and 
leaden  bullets:  have  you  in  the  cups  three  substances  or 
two?  If  you  stir  a  tablespoonful  of  powdered  chalk 
into  a  glass  of  water,  you  obtain  a  milky  fluid  unlike 
either.  Is  it  a  new  substance  or  only  a  mixture  of  the 
two?  Dissolve  a  teaspoonful  of  salt  in  a  glass  of 
water.  The  salt  disappears,  and  we  seem  to  have  only 
one  substance,  namely,  the  water,  left.  Have  we  really 
one  or  two?  Is  brine  a  new  substance,  or  a  mixture  of 
two? 

Simple  as  these  questions  appear  they  neverthe- 
less have  an  important  bearing  upon  our  study.  In 
the  case  of  the  leaden  bullets  and  iron  balls,  we  evi- 
dently have  no  new  substance,  for  we  can  easily  sepa- 
rate the  two.  In  the  case  of  the  chalk  and  water  the 
decision  is  not  so  immediate,  but  if  we  allow  the 
mixture  to  stand,  the  particles  of  chalk  settle  at  the 
bottom,  and  the  two  substances  separate  themselves. 
The  brine  may  seem  more  puzzling,  but  if  we  evapor- 
ate the  water  we  can  recover  all  the  salt.  The  main 
difference  between  the  three  cases  is  that  the  particles 
of  the  substances  mixed  are  united  more  closely  in  one 
case  than  in  another.  In  every  instance  the  test  is  to 
find  whether  we  can  separate  the  mixture  into  the  sim- 
ple substances,  or  "elements"  of  which  it  is  composed. 

Most  of  the  things  we  see  are  compounds.  A  sub- 
stance so  simple  that  it  cannot  be  separated  into  other 
substarices,nor  be  shown  to  be  made  of  other  substances, 
is  called  an  element.  Chemists  recognize  at  present 
between  sixty  and  seventy  elements;  but  the  number  i* 


IS  WATER  AN  ELEMENT?  47 

not  settled  by  any  means.  It  has  often  happened  that 
a  substance  which  has  for  many  years  been  considered 
elementary  has  been  found,  after  all,  capable  of  sepa- 
ration, or  "analysis,"  into  simpler  substances;  while 
every  little  .while  new  substances  are  discovered  which 
have  to  be  added  to  the  list  of  elements  until,  and  unless, 
they  can  be  proved  to  be  compounds. 

On  the  whole,  as  our  power  of  analysis  increases,  the 
tendency  is  to  reduce  rather  than  enlarge  the  number 
of  elements;  and  there  are  some  who  are  even  asking 
whether,  after  all,  those  ancient  philosophers  may  not 
have  been  right,  who  held  that  all  the  forms  of 
matter  were  derivable  from  some  one,  though  undeter- 
mined, element. 

From  all  this  you  will  perceive  that  analysis,  or  the 
separation  of  mineral  compounds  into  their  elements,  is 
one  of  the  most  important  means  of  learning  their  true 
character.  In  evident  mixtures,  like  that  of  iron  balls 
and  lead  bullets,  the  analysis  consists  merely  in  the  act 
of  picking  out  one  kind,  and  leaving  the  other.  In  the 
case  of  solids  held  in  liquids  but  not  dissolved,  the  analy- 
sis often  results  by  the  process  of  settling;  and  in  the 
case  of  solutions  by  evaporation  or  distillation.  Certain 
compounds  of  iron  can  be  ana'yzed  by  heat.  A  mix- 
ture of  iron-filings  and  sand  can  be  analyzed  by  holding 
a  magnet  near  it;  the  iron  is  drawn  to  the  magnet,  and 
the  sand  left  behind. 

Some  substances  are  resolved  into  their  elements  by 
a  current  of  electricity. 

A  few  hundred  years  ago  water  was  believed  to  be  an 


4«  THE   WORLD   OF  MATTER. 

element.  "Fire,  water,  earth,  and  air,"  were  said  to  be 
"the  four  elements,"  of  which  the  whole  earth  is  com- 
posed. 

Let  us  now  make  a  few  experiments  with  a  view  to 
learning  whether  this  ancient  opinion  of  water  is 
correct. 

So  far  as  we  can  perceive  by  the  most  careful  exam- 
ination of  pure  water  under  ordinary  conditions,  it  is  a 
simple  substance.  The  eye  detects  no  mixture,  and 
nothing  is  revealed  either  to  taste  or  smell. 

No  matter  how  long  we  may  allow  it  to  stand,  there 
is  no  separation  into  simpler  substances  either  by  settling 
or  evaporation.  If  we  boil  it  and  condense  its  vapor, 
we  get  again  the  same  quantity  of  the  same  substance, 
pure  water,  and  nothing  else.  The  approach  of  a 
magnet  produces  no  perceptible  effect. 

Let  us  try  electricity.  The  following  experiment  is 
more  difficult  than  any  I  have  before  described,  but 
with  a  little  care  and  patience  you  can  perform  it  suc- 
cessfully, and  the  result  is  so  surprising,  so  beautiful,  and 
so  instructive,  that  you  cannot  afford  to  neglect  it. 

Before  attempting  it,  however,  we  must  learn  some 
of  the  simpler  facts  about  this  wonderful  form  of  force. 

Cut  out  a  piece  of  sheet  zinc  as  large  as  a  silver  half- 
dollar.  Place  this  under  your  tongue,  and  place  the 
silver  half-dollar  on  your  tongue.  Now  bring  the  for- 
ward edges  of  the  zinc  and  silver  together. 

Do  you  feel  anything?  This  peculiar  tingling  sen- 
sation is  produced  by  a  current  of  electricity,  which 
passes  through  your  tongue  from  the  zinc  to  the  silver, 


iS  WATER  AN  ELEMENT?  49 

and  back  again  to  the  zinc,  at  the  point  where  the  two 
metals  touch  each  other  in  front,  This  course  of  the 
//p.-.*-.-,  electricity  is  called  an  electric  cir- 

((      i    I  cuit,  and  such  a  circulating  cur- 

rent is  set  in  motion  whenever 
two  different  metals  are  placed  in 
any  acid,  and  joined  together  out- 
side the  acid,  either  by  being 
brought  into  contact  directly,  or 
by  means  of  Connecting  wires. 
To  illustrate  this  more  clearly, 
F'g-  I0  fill  a  glass  or  earthen  jar  with 

dilute  sulphuric  acid,  and  immerse  in  the  liquid  at  a  little 
distance  from  each  other  a  plate  of  zinc  and  a  plate  of 
copper.  Attach  a  wire  to  the  upper  end  of  each  plate, 
fig.  10. 

Now,  taking  a  wire  in  each  hand,  touch  one  to  the 
upper  and  the  other  to  the  under  surface  of  your 
tongue.  I#  not  the  result  similar  to  that  produced  by  the 
coin  and  the  piece  of  zinc,  though  more  intense?  Bring 
the  ends  of  the  wires  together.  What  is  the  effect? 

This  apparatus  is  of  ten  called  a  "cell."  Many  other 
substances  besides  zinc  and  copper  produce  similar  cur- 
rents. One  of  the  most  common  and  practical  substi- 
tutes for  copper  is  carbon,  a  substance  with  which  you 
are  familiar  in  the  forms  of  charcoal  and  coke,  and  the 
hard  incrustations  which  accumulate  in  gas-retorts.  This 
is  not  the  place,  however,  to  enter  into  a  description  of 
the  numerous  varieties  of  cells  which  have  been  devised. 
They  all  work  on  the  same  principle,  and  can  be 
4 


50  THE  WORLD  OF  MATTER. 

bought  at  a  low  price.  The  combination  of  two  or 
more  cells  is  called  a  "battery."  For  our  present  ex- 
periment you  will  need  a  battery  of  four  or  five  cells; 
and,  if  you  do  not  wish  to  make  them,  you  can  probably 
get  them  at  second  hand  from  any  telephone^exchange 
at  trifling  cost.  The  free  ends  of  the  connecting  wires, 
through  which  the  force  of  the  electricity  manifests 
itself,  are  called  electrodes,  a  Greek  word,  meaning 
"electric  pathways." 

These  ends  are  also  called  "poles,"  a  word  which 
means  in  this  connection  the  points  of  greatest  intensity 
or  tension. 


Fig.  i 


Having  now  provided  your  electric  battery,  fill  a 
glass  vessel  with  water,  to  which,  in  order  to  assist  the 
passage  of  the  electric  current,  some  sulphuric  acid 
must  be  added,  as  pure  water  is  an  imperfect  conductor. 
Fasten  apiece  of  platinum  to  the  end  of  each  wire;  or 
in  other  words,  let  the  connecting  wires  end  in  platinum 
electrodes.  This  is  not  essential,  but  like  the  sulphuric 
acid  greatly  facilitates  the  action  of  the  electricity.  Put 
the  electrodes  in  the  water,  and  invert  over  each  a  glass 


IS  WATER  AN  ELEMENT?  51 

tube  filled  with  water,  fig.  n,  in  which  O  and  H  are 
the  tubes,  C  the  wire  coming  from  the  copper  or 
carbon,  Z  the  wire  coming  from  the  zinc,  and  E  E, 
the  electrodes. 

On  the  passage  of  a  current  of  electricity,  bubbles 
are  seen  to  rise  from  each  electrode.  The  water  gradu- 
ally falls  in  the  tubes,  and  that,  too,  without  perceptibly 
rising  in  the  large  vessel.  It  looks  as  if  the  current 
were  boiling  the  water  and  filling  the  tubes  with  steam. 
But,  look  again.  The  effect  in  the  two  tubes  is  not  the 
same.  In  one  the  apparently  empty  space  above  the 
water  is  twice  as  great  as  in  the  other;  and  yet  (he  water 
in  that  tube  does  not  seem  to  "boil"  any  faster  than  that 
in  the  other. 

At  all  events  we  are  rapidly  losing  sight  of  our  water. 
Let  us  carefully  examine  the  apparently  empty  tubes 
to  ascertain  whether  it  can  be  hiding  there. 

We  will  first  determine  whether  they  are  full  of 
steam.  Placing  the  hand  on  them  we  find  them  cold; 
this  proves  that  steam  is  not  present,  and  indeed  a  little 
reflection  would  have  convinced  us  of  this,  from  the 
fact  that  the  tubes  were  neither  burst  nor  forced  out  of 
the  water,  nor  clouded  with  condensing  vapor. 

Are  they  empty  then? 

Light  a  match  or  taper,  and  blow  it  out,  leaving  the 
end  aglow.  Remove  the  tube  O  from  the  water,  first 
placing  your  finger  over  the  opening  of  the  tube,  and 
holding  it  closed  until  you  have  turned  its  mouth  up- 
ward, and  thrust  the  glowing — not  blazing — end  of  the 
taper  into  it.  The  glowing  taper  suddenly  bursts  into 


5*  tHE   WORLD   OF  MATTER. 

flame,  and  burns  vividly.  In  fact  this  tube  is  filled  with 
a  remarkable  sort  of  gas,  which  we  shall  soon  study 
more  in  detail.  For  the  present  it  is  enough  to  know 
that  it  has  been  separated  from  the  water  by  electricity 
at  the  electrode  which  is  connected  with  the  copper  in 
the  battery ;  that  it  causes  other  substances  to  burn  very 
brilliantly,  and  that  its  name  is  Oxygen. 

Now  remove  the  other  tube,  holding  its  mouth  down- 
ward, and  apply  a  lighted  match.  This  tube,  too,  is 
evidently  filled  with  gas,  but  of  a  different  sort,  for  it 
catches  fire  at  the  mouth  of  the  tube,  and  burns  with  a 
flame  which  is  pale  and  bluish,  but  very  hot.  This  gas 
also  we  shall  study  later,  contenting  ourselves  just  now 
with  the  knowledge  that  the  electricity  sets  it  free  from 
the  water  at  the  electrode  which  is  attached,  to  the  zinc, 
that  there  appears  to  be  twice  as  much  of  it  as  there 
was  of  the  oxygen,  that  it  burns  with  a  pale,  hot  flame, 
and  that  its  name  is  Hydrogen;  a  Greek  word,  which 
means  ua  producer  of  water." 

If  the  current  of  electricity  were  continued  long 
enough,  all  the  water  would  be  separated  into  these  two 
gases,  which,  moreover,  always  exist  in  the  water  in  a 
constant  proportion,  namely,  one  volume  of  oxygen  to 
two  volumes  of  hydrogen.*  In  order  to  prove  the 
correctness  of  this  analysis,  we  must  ascertain  whether 
we  can  produce  water  again  by  recombining  the  two 
gases.  If  they  arc  mixed  in  the  proper  proportions, 
they  form  at  first  a  merely  mechanical  mixture  like 

*  Recent  experiments  by  Professor  Morley  show  that  water  contains  2.0002 
parts  of  oxygen  to  i  of  hydrogen. 


IS  WATER  AN  ELEMENT?  S3 

that  of  coal  gas  and  common  air;  but  the  moment  a 
flame  is  applied,  a  much  closer  union  is  brought  about 
< — in  fact,  a  chemical  combination  occurs — accompanied 
by  a  violent  explosion,  arid  in  place  of  the  two  com- 
mingling gases  we  have — water. 

This  experiment  must  be  made  only  with  a  small 
quantity  of  the  gases,  such  as  can  be  contained  in  a 
test-tube,  for  on  a  larger  scale  it  is  dangerous. 

It  is  possible,  however,  to  cause  oxygen  and  hydro- 
gen to  combine  quietly,  by  bringing  them  in  tubes  from 
separate  receptacles  into  a  common  burner.  The 
grandest  experiment  of  this  nature,  according  to  Pro- 
fessor Huxley,  was  made  by  three  eminent  French 
chemists.  It  continued  from  the  i$th  to  the  22d  of 
May,  1790.  During  this  time  the  apparatus  was  con- 
stantly watched,  the  experimenters  sleeping  alternately 
on  mattresses  in  the  laboratory ;  25,96^.  cubic  inches  of 
hydrogen,  and  12, 571- of  oxygen  were  consumed,  and 
the  union  of  these  gases  produced  7»244  grams  of 
water. 

It  is  a  startling  thought  that  all  the  water  on  the 
globe  has  been  formed  at  some  time  or  other  by  the 
union  of  oxygen  and  hydrogen,  which  in  their  free 
state  are  known  only  in  the  physical  condition  of  gases. 

QUESTIONS    ON    CHAPTER    IV. 

1.  In  what  three  states  does  water  exist? 

2.  Find  by  experiment  two  other  substances  that  re- 
semble water  in  this. 

3.  What  is  an  element? 


54  THE   WORLD   OF   MATTER. 

4.  What  is  analysis?     Give  an  illustration. 

5.  Describe  an  electric  cell ;  a  battery. 

6.  What  are  electrodes ?     Poles? 

7.  What  is  added  to  water-  before  testing  the  effect 
of  electricity  upon  it  ?     Why  ? 

8.  Describe  the  effect  of  an  electric  current  on  water. 

9.  What  two  gases  are  obtained  from  water  ? 

10.  In  what  proportions  are   they  combined  to  form 
water? 

11.  How  can  they  be  distinguished? 

12.  How  can  they  be  combined? 


FIRE.  55 


CHAPTER  V. 

FIRE. 

t 

In  the  previous  chapter,  we  learned  by  our  experi- 
ments that  it  would  be  quite  wrong  to  regard  water 
as  an  element,  for  by  a  current  of  electricity  we  ana' 
lyzed  it  into  two  gases,  oxygen  and  hydrogen. 

We  also  learned  that  at  a  high  temperature  thes^ 
two  gases  unite  with  a  hot  flame,  and  return  again  to 
the  form  of  water. 

These  are  among  the  most  beautiful  and  significant 
phenomena  in  nature;  and,  with  those  we  have  before 
studied,  give  us  a  key  to  the  intelligent  understanding 
of  the  whole  world. of  matter.  We  have  been  led  to 
the  discovery  of  two  of  the  most  important  elements  in 
the  world;  we  have  learned  the  nature  of  an  element; 
and  we  can  now  understand  that  every  material  object 
consists  either  of  such  an  element  alone,  or  in  a  state  of 
simple  mixture  with  other  elements,  or  in  a  more  inti- 
mate union  with  other  elements  in  the  form  of  a  chemi- 
cal compound.  We  have  seen  that  mixtures  can  be 
mechanically  separated ;  and  that,  in  the  case  of  water, 
even  the  bands  of  chemical  union  can  be  loosed  by  the 
force  of  electricity ;  and  we  have  learned,  finally,  that 
elements  can  be  caused  to  unite  chemically,  and  that,  in 
the  case  of  oxygen  and  hydrogen,  this  union  is  accom- 


56  THE  WORLD   OF  MATTER. 

panied    by   light  and    heat.     Such    a    combination   is 
termed  combustion,  or  burning. 

Whenever  you  see  fire,  therefore,  you  may  be  cer- 
tain that  a  rapid  combination  of  at  least  two  elementary 
substances  is  taking  place.  From  this  you  will  perceive 
that  the  old  notion  that  fire  is  an  element  was  also  in- 
correct. 

Let  us  now  continue  our  experiments  with  a  view 
to  learning  whether  oxygen  will  combine  with 
other  substances  than  hydrogen.  Tip  the  end  of 
a  bundle  of  fine  iron  wire  with  burning  sulphur,  and 
plunge  it  into  a  jar  of  oxygen.  Do  not  let  the  surpris- 
ing brilliance  of  the  result  distract  your  thought  from 
the  lesson.  The  most  brilliant  teachers  are  not  always 
the  best.  Turn  your  attention  from  the  strange  sight 
of  the  blazing  iron,  to  the  dull  results  of  the  bright 
combustion.  Notice  that  when  the  fire  ceases  the 
oxygen  is  gone  and  the  iron  is  gone:  they  are  "burned 
up."  Are  they  then  destroyed?  No  more  than  the  water 
was  destroyed  which  we  "boiled  away."  The  dark, 
cindery-looking  stuff  in  the  jar  is  the  hiding-place  of 
both;  rather  it  is  both,  chemically  combined. 

That  you  may  be  convinced  that  this  is  true,  you 
should  repeat  the  experiment  more  carefully,  taking 
such  precautions  as  will  assure  you  that  none  of  the 
oxygen  escapes  from  the  jar  during  the  combustion,  and 
that  nothing  else  gets  in  except  the  oxygen  and  the 
iron,  and  the  small  bit  of  sulphur  used  to  heat  the  iron. 
You  must  also  determine  the  exact  weight  of  the 
oxygen  and  of  the  iron  consumed,  and  of  the  substance 


FIRE.  57 

left  after  their  combustion.  If  you  do  this  accurately, 
and  if  you  find  as  other  experimenters  have  found  that 
the  weight  of  the  iron  burned  added  to  the  weight  of 
the  oxygen  used  up  is  exactly  equal  to  the  weight  of  the 
substance  left  after  combustion,  you  can  hardly  doubt 
that  the  latter  is  formed  by  the  union  of  the  oxygen 
and  the  iron.  Substances  formed  by  combustion  with 
oxygen  are  called  oxides  ;  and  this  compound  of  oxygen 
and  iron  is  called  iron  oxide. 

The  heat  of  combustion  is  the  result  of  the  chemical 
combination,  and  the  light  is  due  to  the  heat.  The  heat 
is  caused  by  the  friction  of  the  little  particles  of  the 
combining  substances  as  they  are  forcibly  drawn  to- 
gether; just  as  an  anvil  is  heated  by  hard  blows  from  a 
hammer.  The  more  rapid  the  combustion  the  greater 
the  heat.  Oxygen  and  iron  are  combining  slowly  at 
ordinary  temperatures  whenever  iron  grows  rusty;  and 
the  iron-rust  is  an  oxide  of  iron. 

I  said  you  should  weigh  your  oxygen.  Let  me 
show  you  how.  Y*ou  need  a  glass  or  globe  holding 
three  or  four  quarts,  the  neck  of  which  is  closed  by  an 
air-tight  stop-cock,  and  adapted  to  be  screwed  to  the  plate 
of  an  air-pump.  The  air  is  then  pumped  out,  and  the 
weight  of  the  empty  globe  ascertained  by  a  delicate 
balance.  Oxygen  is  now  allowed  to  enter,  and  the 
globe  again  weighedy  The  difference  in  weight  will 
be  the  weight  of  that  quantity  of  oxygen ;  and  knowing 
this,  you  can  calculate  the  weight  of  any  other  quantity 

It  may  save  you  trouble,  however,  to  know  that  & 
pint  of  oxygen  weighs  iiy5^-  grains,  and  a  cubic  foo 


58  THE  WORLD   OF  MATTER. 

13^  ounces.  (Faraday).  Oxygen  is  nearly  sixteen 
times  as  heavy,  bulk  for  bulk,  as  hydrogen,  which  is 
the  lightest  element  known;  so  that,  although,  as  you 
remember,  we  obtained  twice  as  much  hydrogen  from 
water,  yet  the  oxygen  was  nearly  eight  times  as  heavy 
as  the  hydrogen;  in  other  words,  if  we  reckon  by 
weight,  instead  of  bulk,  oxygen  makes  up  f  of  water, 
and  hydrogen  only  J. 

I  am  glad  to  come  back  in  this  way  to  water,  for  I 
think  this  is  just  the  right  time  for  you  to  make  another 
experiment  with  it;  one  that  you  could  not  have  un- 
derstood so  clearly  before  you  saw  the  oxygen  and 
iron  uniting  by  combustion,  and  forming  the  black 
oxide  of  iron. 


Fig.  12. 

For  the  experiment  you  will  need  apparatus  arranged 
practically  as  shown  in  Fig.  12.  A  is  a  flask  for  boil- 
ing water  over  an  alcohol  lamp;  C  a  small  furnace; 
B  B,  a  tube  about  an  inch  in  diameter  passing  through 
the  furnace;  D,  a  jar  of  water  inverted  in  a  vessel  of 
water,  E.  The  tube  BB  may  be  a  gun-barrel,  a  piece 


FIRE.  59 

of  gas-pipe,  or  preferably  a  porcelain  tube,  and  is  filled 
with  iron  turnings  or  fine  bright  iron  wire.  The  heat  of 
the  lamp  boils  the  water  and  converts  it  into  steam. 
.The  steam  passes  through  the  red-hot  tube,  and  bubbles 
arising  through  the  water  are  caught  in  the  upper  part 
of  the  jar  D.  When  all  the  water  in  this  tube  has  been 
expelled,  you  will  know  that  its  place  has  been  taken 
by  some  sort  of  gas.  Is  it  steam?  No,  for  it  is  cold. 
Testing  it  with  a  match  you  find  that  it  catches  fire 
and  burns  at  the  mouth  of  the  tube  with  a  pale  blue 
flame.  You  recognize  hydrogen;  and  you  perceive 
that  in  passing  through  the  furnace,  the  steam  has 
parted  with  its  oxygen.  Recollecting  the  experiment 
of  burning  iron  with  oxygen,  you  now  readily  under- 
stand that  what  you  saw  going  on  so  brilliantly  in  the 
jar  has  taken  place  unobserved  in  the  red-hot  tube; 
namely,  the  oxygen  of  the  water  has  combined  with 
the  iron  in  the  tube,  and  the  hydrogen  has  passed  on 
alone  into  the  jar  D. 

When  the  tube  BB  becomes  cool,  you  will  find  in  it 
the  same  dark-colored  substance  that  you  found  when 
the  oxygen  and  iron  combined  in  the  jar;  namely,  iron 
oxide. 

This  experiment  is  commonly  made  to  illustrate  a 
method  of  obtaining  hydrogen,  but  we  have  used  it  to 
impress  more  firmly  upon  our  minds  the  manner  in 
which  a  chemical  union  takes  place  between  oxygen 
and  heated  iron;  and  to  illustrate  the  new  fact  that  the 
tendency  to  this  combination  is  so  strong  that  it  not  only 
occurs  when  heated  iron  is  plunged  into  pure  oxygen, 


6o 


THE  WORLD   OF  MATTER. 


but  that  the  oxygen  in  water   will    separate    from  the 
hydrogen  in  order  to  unite  with  the  iron. 

It  is  an  important  fact  that  a  stronger  attraction  ex- 
ists between  particles  of  heated  iron  and  oxygen,  than 
between  particles  of  oxygen  and  hydrogen.  A  like 
principle  controls  the  combination  of  all  the  other  ele- 
ments; they  manifest  apparent  preferences  in  their 
combinations,  somewhat  as  young  people  do  in  their 
choice  of  partners ;  and  by  learning  what  these  prefer- 
ences are,  and  taking  advantage  of  them  we  can  effect 
many  innocent  divorces,  such  as  that  we  have  just 
caused  between  hydrogen  and  oxygen,  and  bring  about 
many  not  unhappy  marriages  like  the  one  just  effected 
between  oxygen  and  irpn. 


•  13- 


This  special  attraction  existing  between  certain  ele- 
ments is  called  chemical  affinity. 

Substances  which  combine  at  certain  temperatures 
may  often  be  separated  again  by  increasing  the  heat. 
Thus  the  iron  oxide  which  we  have  obtained  can  be  so 


FIRE.  61 

intensely  heated  as  to  be  resolved  again  into  its 
elements;  but  so  great  heat  is  required  that  the  experi- 
ment is  difficult.  A  similar  compound  of  mercury  and 
oxygen,  however,  known  as  oxide  of  mercury,  can 
be  very  readily  separated  by  heat;  and  affords  us 
a  practical  method  of  obtaining  oxygen  for  our  experi- 
ments. 

For  this  purpose  apparatus  should  be  arranged  as  in 
Fig.  13,  which  needs  no  explanation. 

The  most  convenient  and  rapid  method  of  preparing 
oxygen,  when  a  considerable  quantity  is  required,  is  to 
heat  a  mixture  of  equal  parts  of  potassium  chlorate  and 
black  oxide  of  manganese. 

Potassium  chlorate  contains  three  elements,  oxygen, 
chlorine,  and  potassium,  two  of  which  are  as  yet 
strange  to  you.  Oxide  of  manganese,  as  its  name  im- 
plies, is  a  compound  of  oxygen  with  another  unfamiliar 
element,  manganese.  We  do  not  care  to  study  these 
new  elements  at  present;  it  is  sufficient  to  know  that 
oxygen  is  combined  with  them,  and  can  readily  be  dis- 
engaged  by  heating. 

Experiment. — Mix  an  ounce  of  potassium  chlorate 
with  an  equal  weight  of  coarsely  powdered  oxide  of 
manganese  in  a  mortar.  Heat  a  little  of  the  mixture 
in  a  test-tube  before  using,  because  the  oxide  of  manga- 
nese is  sometimes  impure,  and  may  then  cause  explo- 
sions if  mixed  with  potassium  chlorate  and  heated.  If 
the  substances  separate  quietly  in  the  tube,  you  may 
safely  proceed  with  the  experiment  on  a  larger  scale, 
by  heating  the  mixture  in  a  glass  retort  as  shown  in 


62  THE  WORLD  OF  MATTE&. 

Fig.    14,    and    collecting    the    oxygen   over   water   as 
usual.     The  retort,  however,  frequently  cracks. 


Having  thus  collected  as  much  oxygen  as  you  wish, 
exercise  your  ingenuity  in  trying  all  sorts  of  experi- 
ments with  it.  So  long  as  you  do  not  mix  hydrogen 
with  it,  it  is  quite  safe.  Smell  it,  taste  it,  breathe  it, 
burn  all  sorts  of  substances  in  it  (by  the  way  it  will 
combine  with  almost  every  thing  in  the  world),  blow 
soap-bubbles  with  it,  and  see  whether  they  rise  or  fall ; 
put  bits  of  cold  iron  in  it,  and  leave  them  for  a  few  days 
to  see  whether  any  combination  takes  place  without 
heat;  in  a  word,  get  acquainted  with  oxygen,  so  that 
you  can  recognize  it  wherever  you  meet  it,  and  so  that 
you  can  recognize  its  effects  even  when  you  do  not 
detect  its  presence. 


FIRE.  63 

It  will  take  some  time,  but  you  can  well  afford  it, 
just  as  I  can  well  afford  to  give  large  space  to  it  in  this 
little  book.  It  is  the  most  important  element  in  the 
world.  It  is  eight-ninths  of  all  our  water,  it  consti- 
tutes one-half  the  solid  crust  of  the  earth,  it  makes  up 
four-fifths  of  the  weight  of  all  our  herbs  and  shrubs 
and  trees,  and  three-fourths  of  your  own  body,  and 
of  the  bodies  of  all  animals,  and  it  is  the  chief  source 
of  fire.  We  walk  on  it,  and  burn  it,  and  eat  it,  and 
drink  it,  and  breathe — 

Ah!  but  I  did  not  mean  to  tell  you  just  yet  that 
one-fifth  of  all  the  air  is  oxygen.  I  meant  to  let  you 
find  it  out  by  degrees.  But,  never  mind,  it  is  true, 
and  we  must  devote  the  next  chapter  to  a  study  of 
the  air.  B-efore  passing  to  that,  however,  I  think  you 
are  entitled  to  know  an  easier  method  of  obtaining  a 
supply  of  hydrogen.  You  should  prepare  enough  to 
enable  you  to  become  as  familiar  with  it  as  with 
oxygen. 

The  most  convenient  process  depends  upon  two  facts: 
first,  that  acids  contain  hydrogen;  second,  that,  as  a  rule, 
when  a  metal  is  placed  in  an  acid,  all  of  the  acid 
except  the  hydrogen  enters  into  new  combinations  in 
which  the  metal  is  taken  up,  leaving  the  hydrogen  free. 

Metals  are  the  successful  rivals  of  hydrogen.  No 
matter  how  well  satisfied  oxygen  and  sulphur  and 
chlorine  and  the  rest  may  appear  to  be  with  hydro- 
gen for  a  partner,  once  let  almost  any  metal  come 
among  them,  and  they  fly  to  it,  leaving  the  hydrogen 
deserted. 


64  THE   WORLD   OF  MATTER. 

To  illustrate  this  fickleness  of  the  elements,  and  at 
the  same  time  to  procure  a  good  supply  of  suffi- 
ciently pure  hydrogen,  try  the  effect  of  a  little  zinc 
upon  that  compound  of  sulphur,  oxygen,  and  hydro- 
gen, known  as  sulphuric  acid. 

Provide  a  jar  fitted  with  a  cork  having  two  holes. 
Through  one  hole  pass  a  funnel. tube,  and  through 
the  other  a  glass  tube  bent  in  convenient  form.  Put 
a  small  handful  of  granulated  zinc,  or  zinc  clippings, 
into  the  jar. 

Prepare  a  mixture  of  sulphuric  acid  and  water  as 
follows:  Into  six  ounces  of  cold  water  pour  very 
slowly  one  ounce  of  ordinary  sulphuric  acid,  keeping 
the  mixture  constantly  stirred.  If  you  pour  it  in 
rapidly  the  heat  evolved  may  be  so  great  as  to  convert 
the  water  into  steam  and  cause  the  strong  acid  to  spat- 
ter. After  the  mixture  has  cooled,  pour  enough  of  it 
through  the  funnel  into  the  jar  to  cover  the  zinc. 

A  brisk  ebullition  occurs  at  once,  so  eager  are  the 
little  particles  of  oxygen  and  sulphur  to  combine  with 
the  zinc,  and  the  deserted  hydrogen  rises  into  the  jar. 
For  two  or  three  minutes  the  jar  will  be  filled  with  a 
mixture  of  hydrogen  and  air;  and  since  one-fifth  of  the 
air  is  oxygen,  this  is  a  highly  explosive  and  dangerous 
mixture,  as  we  have  already  learned. 

Wait  a  few  minutes,  therefore,  until  the  hydrogen 
has  expelled  all  the  air,  and  then  collect  as  much  as  you 
wish  in  the  usual  way  over  water.  Fig.  17. 

You  can  easily  ascertain  whether  all  the  air  has  been 
expelled  by  filling  a  test-tube  with  the  escaping  gas, 


FIRE.  65 

and  observing  whether  it  burns  quietly  when  lighted. 
In  this,  as  in  all  other  experiments  with  hydrogen, 
remember  to  hold  the  jar  containing  it  mouth  down- 
ward; otherwise  it  will  either  escape  or  become  mixed 
with  air,  and  explode  when  ignited.  You  had  better 
collect  several  bottles  of  hydrogen,  for  there  are  many 
interesting  and  instructive  experiments  to  be  made  with 
it.  Invent  as  many  as  you  can.  Burn  a  fine  jet  of  it 
in  air  under  a  bright  dry  glass,  and  notice  how  the  glass 


Fig.  15. 

at  once  becomes  clouded  by  small  drops  of  water  con- 
densed upon  its  surface.  You  readily  understand  from 
this  experiment  that  the  hydrogen  is  combining,  or 
burning,  with  the  oxygen  of  the  air.  Push  a  burning 
taper  up  into  a  jar  of  hydrogen.  It  is  extinguished. 
Blow  soap-bubbles  with  it,  and  you  have  beautiful 
balloons.  These  can  be  blown  by  connecting  a  tobacco, 
pipe  by  a  rubber  tube  to  the  tube  from  which  hy- 
drogen is  driven  by  the  action  of  the  acid  and  zinc. 
Dip  the  bowl  of  the  pipe  in  soap-suds,  and  the  force  of 
the  escaping  gas  should  be  sufficient  to  blow  bubbles. 
5 


66  THE   WORLD   OF   MATTER. 

Finally  blow  some  bubbles  with  a  mixture  of  air  and 
hydrogen,  and  touch  them  with  a  lighted  taper  as  they 
rise,  taking  care,  however,  not  to  light  them  while  on 
the  pipe,  because  the  explosion  might  force  flame  into 
the  jar  and  blow  it  to  pieces. 

Thus  the  oxygen  and  hydrogen  separated  by  the  in- 
truding metal  are  again  united,  and  in  these  most  fairy- 
like,  and  many-colored  balloons  are  floating  away  on 
their  bridal  tour.  A  touch  of  flame  bursts  their  crystal 
car,  but  serves  only  to  render  their  union  more  intimate, 
and  they  fall  together  in  a  sparkling  drop  of  water. 

QUESTIONS  ON  CHAPTER  5. 

1.  What  is  fire? 

2.  With  what    substances    does   oxygen   combine? 
Ans.     All  the  elements  except  fluorine. 

3.  Describe  the  combustion    of  iron  and   oxygen. 
What  is  the  product? 

4.  How  can  a  gas  be  weighed  ? 

5.  What  are  the  effects  of  passing  steam  through  a 
red-hot  tube  filled  with  iron-borings? 

6.  What  is  chemical  affinity  ? 

7.  Describe  a  practical  method  of  obtaining  oxygen. 

8.  Has  oxygen  any  effect  on  cold  iron  ? 

9.  Is  it  heavier  or  lighter  than  air? 

10.  Where  is  it  found  in  nature? 

11.  Is  it  in  the  air? 

12.  Describe  and  explain  the   process  of  obtaining 
hydrogen  by  the  action  of  zinc  upon  sulphuric  acid. 

13.  What  practical  use  is  made  of  hydrogen? 


AIR.  67 


CHAPTER  VI. 

AIR. 

If  you  have  carefully  studied  the  preceding  chapter, 
and  performed  the  experiments  there  described,  you 
have  become  pretty  familiar  with  two  of  the  most  im- 
portant elements.  The  most  characteristic  property  of 
oxygen  is  its  power  of  combustion  with  other  sub- 
stances. You  can  hardly  have  failed  to  nt>tice  that  the 
burning  of  a  candle,  the  flame  of  a  gas-jet,  and  the  fire 
on  the  hearth  all  resemble  the  flame  of  substances  burn- 
ing with  oxygen,  differing  only  in  intensity. 

A  simple  test  of  the  presence  of  oxygen  in  the  air 
is  holding  a  cold  glass  jar  or  a  piece  of  any  cold  metal 
over  the  flame  of  an  alcohol  lamp,  or  over  a  gas  flame. 
Both  alcohol  and  coal  gas  contain  a  large  percentage  of 
hydrogen. 

Presently  you  will  observe  a  dampness  coming  upon 
the  cold  glass  or  metal,  and  this  increases  until  it  stands 
in  drops  and  trickles  down.  On  examination,  you  will 
find  this  liquid  to  be  pure  water.  Now  water  cannot 
be  produced  except  by  combining  oxygen  and  hydro- 
gen. In  this  case  the  hydrogen  comes  from  the  alcohol 
or  gas;  and  it  is  plain  that  the  oxygen  must  come  from 
the  air. 

But  if  air  is  so  largely  composed  of  oxygen,  how  is  it 


68  THE   WORLD   OF  MATTER. 

that  the  air  does  not  cause  the  alcohol  and  tlie  gas  to 
burn  as  brilliantly  as  oxygen  does?  And  why  will  not 
iron  burn  in  the  air?  And  if  oxygen  unites  in  com- 
bustion with  everything  else,  why  is  it  that,  once  a  fire 
gets  started,  particularly  a  great  conflagration  as  of  a 
forest  or  a  <:ity,  it  does  not  increase  and  spread  and 
burn  up  the  whole  world?  Well,  I  have  no  doubt  it 
would  do  that  if  there  were  nothing  but  pure  oxygen 


Fig.  1 6. 

in  the  air.  Nor  would  it  wait  for  a  great  fire  to  start  it, 
for  there  are  substances  like  phosphorus  that  combine 
with  oxygen  at  ordinary  temperatures. 

If  the  air  were  pure  oxygen,  such  substances  would 
kindle  first,  and  they  would  serve  as  a  match  to  set  the 
world  on  fire.  Iron  buildings  would  blaze  more  fiercely 
than  wooden  ones.  That  would  be  a  grand  holiday  for 
the  fire-spirits! 

"The  elements  would  melt  with  fervent  heat,  and  the 
heavens  would  be  rolled  together  like  a  scroll." 


AIR.  69 

This  terrible  result  is  prevented  only  by  the  con- 
trolling presence  of  another  element  in  the  air,  which 
holds  the  fiery  oxygen  in  check,  and  compels  it  to  com- 
bine as  a  rule  in  a  reasonably  temperate  and  safe  com- 
bustion. 

Let  us  see  whether  we  can  unmingle  a  little  air  and 
procure  some  of  this  wonderful  gas  which  alone  saves 
the  world  from  bursting  into  flames. 

Float  a  light  porcelain  dish  on  water  in  a  glass  or 
earthen  basin.  Put  a  small  piece  of  phosphorus  in  the 
floating  dish,  and  light  it.  Cover  the  dish  with  a  large 
jar. 

The  phosphorus  at  once  combines  with  the  oxygen  of 
the  air,  forming  a  phosphorus  oxide,  at  first  appear- 
ing in  the  form  of  a  white  cloud,  which,  however, 
soon  dissolves.  When  the  jar  which  has  become  heated 
by  the  burning  of  the  oxygen  and  phosphorus  becomes 
cool,  you  will  notice  that  one-fifth  of  that  part  of  the 
jar  that  was  before  filled  with  air  is  filled  with  water, 
which  has  risen  in  it  from  the  basin. 

You  may  now  test  the  contents  of  the  upper  four- 
fifths  of  the  jar.  It  cannot  be  empty,  or  the  weight  of 
the  atmosphere  would  press  the  water  from  the  basin 
up  into  it  and  fill  it  completely.  It  cannot  be  steam,  for 
it  is  cold.  It  cannot  be  hydrogen,  for  it  will  not  burn. 
It  is  not  oxygen,  for  a  lighted  taper  thrust  into  it,  in- 
stead of  blazing  more  brightly,  is  immediately  extin- 
guished. It  has  no  color,  taste,  or  smell.  It  is  com- 
pletely inactive.  No  action  short  of  the  most  in- 
ten.e  electric  force  can  ca.use  it  to  combine  chemically 


70  THE  WORLD  OF  MATTER. 

with  oxygen.     It  is  a  perfectly  safe  substance,  under 
ordinary  conditions;  and  its  name  is  Nitrogen. 

But  this  quietness  is  no  indication  of  lack  of  power. 
"Deep  rivers  run  still."  It  takes  a  man  of  considerable 
strength  of  character  to  live  quietly  among  noisy 
neighbors,  particularly  if  he  succeeds  in  keeping  them 
moderately  quiet  too.  So,  lest  you  should  feel  any  con- 
tempt for  this  most  reserved  and  indifferent  gas,  I  must 
warn  you  that  on  due  occasion  it  enters  into  combination 


Fig.   17. 

with  other  elements,  and  manifests  the  most  sudden  and 
unexpected  activity.  Thus  when  under  the  influence  of 
electricity,  or  by  the  decay  of  plants  and  animals,  ni- 
trogen is  forced  to  unite  with  hydrogen,  it  forms 
ammonia  and  in  this  form  possesses  a  pungency  and 
caustic  flavor  that  quite  compensate  for  its  ordinary 
lack  of  smell  and  taste.  Pure  ammonia  is  a  colorless 
gas  which  is  very  soluble  in  water.  The  "liquor 
ammoniae"  of  the  drug-stores  is  a  solution  of  this  gas 
in  water,  prepared  as  shown  in  Fig.  17,  by  passing 


AIR.  71 

the  gas  into  a  flask  containing  water  and  kept  cool 
by  being  placed  in  a  large  vessel  of  cold  water.  This 
is  necessary,  because  considerable  heat  is  caused  by  the 
dissolving  gas. 

When  nitrogen  is  combined  with  a  gas  called  chlorine 
it  forms  one  of  the  most  dangerous  and  explosive  com- 
pounds known. 

Dulong,  the  chemist  who  discovered  it  in  i8n,lost 
one  eye  and  three  fingers  for  his  pains,  and  two  years 
later  Faraday  and  Davy  although  on  their  guard  met 
a  similar  accident.  "Knowing  that  the  liquid  would  .go 
off  on  the  slightest  provocation,  the  experimenters  wore 
masks  of  glass,  but  this  did  not  save  them  from  injury. 
In  one  case,  Faraday  was  holding  a  small  tube  contain- 
ing a  few  grains  of  it  between  his  finger  and  thumb, 
and  brought  a  piece  of  warm  cement  near  it,  when  he 
was  suddenly  stunned,  and  on  recovering  consciousness, 
found  himself  standing  with  his  hand  in  the  same  po- 
sition, but  torn  by  the  shattered  tube,  and  the  glass  of 
his  mask  even  cut  by  the  projected  fragments.  Nor  was 
it  easy  to  say  when  the  compound  could  be  relied  on, 
for  it  seemed  very  capricious;  for  instance,  one  day  it 
rose  quickly  in  vapor  in  a  tube  exhausted  by  the  air- 
pump,  but  on  the  next  day,  subjected  to  the  same  treat- 
ment, it  exploded  with  a  fearful  noise,  and  injuring  Sir 
Humphrey  Davy." 

The  name,  nitrogen,  signifies  a ''producer  of  niter," 
and  is  applied  to  this  gas  because  it  is  one  of  the  principal 
elements  in  niter,  or  "saltpeter."  Niter  is  formed  by 
the  combination  of  nitrogen  with  oxygen  and  potassium. 


72  THE    WORLD    OF   MATTER. 

It  is  found  in  long,  colorless,  six-sided  crystals,  marked 
by  fine  parallel  lines  or  "strice."  Minerals  so  marked 
are  called  "striated."  It  has  a  strong  salty  taste,  and 
can  readily  be  dissolved  in  water.  It  occurs  as  a  natural 
product  in  the  East  Indies,  Egypt,  and  Persia.  It  is 
found  in  the  juices  of  various  plants,  as  the  sunflower 
nettle,  tobacco,  and  barley. 


Fig.  18. 

Niter  is  used  in  the  manufacture  of  sulphuric  and 
nitric  acids,  as  an  ingredient  of  fireworks,  and  esoecially 
in  the  manufacture  of  gunpowder. 

It  is  extensively  used  in  medicine,  particularly  in 
acute  cases  of  rheumatism,  in  certain  affections  of  the 
throat,  and  in  spasmodic  asthma. 

Nitric  acid  is  an  important  compound  of  nitrogen, 
oxygen,  and  hydrogen,  and  in  one  form,  in  which  water 
also  is  present,  is  known  as  aqua-fortis.  It  is  astonish- 


AIR.  73 

ing  that  these  two  elements,  which  when  simply  mixed 
form  the  air  we  breathe,  when  chemically  combined, 
make  an  acid  so  powerful  and  destructive. 

If  a  large  glass  globe  filled  with  dry  air  be  connected 
with  an  electric  battery  and  an  "induction  coil,"  as 
shown  in  Fig.  18,  and  sparks  be  passed  through  the 
air  in  the  globe,  red  fumes  are  rapidly  formed.  On 
pouring  a  few  drops  of  water  into  the  globe  and 
shaking  it,  the  red  fumes  are  absorbed  by  the  water, 
and  nitric  acid  is  the  result. 

When  a  flash  of  lightning  passes  through  the  air  the 
same  effect  is  produced,  and  this  accounts  for  the  pres- 
ence of  a  certain  amount  of  nitric  acid  in  the  atmosphere. 

When  nitric  acid  is  exposed  to  the  air  it  gives  off 
strong  fumes  which  are  dangerous  to  breathe.  The 
pure  acid  absorbs  moisture  very  rapidly.  It  is  ex- 
tremely corrosive;  for  example,  when  dropped  on  the 
hand  it  produces  painful  wounds,  and  colors  the  skin 
yellow  or  brown. 

Nitric  acid  is  used  in  the  formation  of  coal-tar  colors, 
in  the  manufacture  of  gun-cotton,  nitro-glycerine,  and 
dynamite,  and  in  nitrate  of  silver,  which  is  so  widely 
used  by  photographers. 

This  acid  has  a  powerful  effect  upon  sulphur,  phos- 
phorus, carbon,  tin,  and  many  othei  substances,  the 
oxygen  contained  in  it  uniting  rapidly  with  these  ele- 
ments and  "oxydizing"  them.  Pour  a  little  nitric  acid 
upon  granulated  tin  and  study  the  result.  The  white 
powder  which  is  deposited  is  an  oxide  of  tin. 

When  cotton-wool  is  soaked  in  a  mixture  of  strong 


74  THE   WORLD   OF  MATTER. 

nitric  acid  and  sulphuric  acid,  washed,  and  dried,  it 
becomes  "gun-cotton,"  an  explosive  so  powerful,  that 
when  used  in  shells  it  is  six  times  as  effective  as  the 
same  weight  of  gunpowder.  No  smoke  accompanies 
its  explosion,  and  for  this  reason  it  has  been  very  useful 
in  mining.  Other  advantages  are  that  time,  dampness, 
and  exposure  to  air  do  not  injure  it;  it  occupies  a  com- 
paratively small  space,  is  light,  and  is  not  liable,  as  gun- 
powder is,  to  accidents  from  spilling.  Dynamite  and 
other  more  recently  invented  compounds  have,  however, 
now  largely  taken  the  place  of  gun-cotton. 

Another  curious  compound  of  nitrogen  and  oxygen 
must  be  mentioned,  differing  from  nitric  acid  in  the 
proportions  of  the  two  gases,  and  in  the  absence  of 
hydrogen.  It  is  called  "nitrous  oxide,"  and  is  remark- 
able for  the  effects  it  produces  when  breathed. 

These  are  Jirst,  "singing"  in  the  ears,  then  insensi- 
bility, and  then,  if  the  breathing  be  continued,  death. 
When  one  volume  of  oxygen  is  mixed  with  four  vol- 
umes of  nitrous  oxide,  the  mixture  is  called  "laughing 
gas,"  and  the  effect  of  inhaling  it  is  less  serious.  It 
causes  temporary  insensibility  during  which  minor 
surgical  operations,  such  as  the  extraction  of  teeth,  may 
be  performed  without  pain.  The  effect  soon  passes  off 
and  does  no  harm.  Owing  to  the  liability  of  having 
impurities  mingled  with  this  gas,  it  is  dangerous  for 
amateurs  to  experiment  with  it. 

These  are  but  a  few  of  the  many  interesting  com- 
pounds of  nitrogen,  and  are  given  to  illustrate  how  an 
element  which,  when  pure,  appears  to  be  the  nearest 


.       AIR.  ^  75 

possible  approach  to  nothing  at  all,  having  no  color, 
taste,  or  smell,  being  incapable  of  burning,  or  support- 
ing combustion,  and  unable  to  support  life,  becomes, 
when  combined  with  other  elements,  suddenly  endowed 
with  the  most  intense  energy;  helping  to  produce  the 
most  vivid  colors,  the  most  acid  taste,  the  most  pungent 
smell,  the  most  violent  explosions,  and  the  most  nec- 
essary constituents  of  food. 

To  illustrate  the  importance  of  nitrogen  in  food, 
it  may  be  stated  that  it  occurs  abundantly  in  all 
flesh,  eggs,  and  cheese,  and  is  an  essential  ingredient 
of  all  foods  directly  adapted  to  produce  blood  and 
muscle. 

I  have  refrained  from  giving  minute  directions  for 
obtaining  the  various  compounds  of  nitrogen,  as  their 
preparation  and  use  involve  too  much  danger;  but  if 
you  have  attentively  performed  the  few  simple  experi- 
ments given,  you  must  by  this  time  have  become  rea- 
sonably familiar  with  this  most  fascinating  element. 

How  largely  does  the  beauty,  the  power,  the  life, 
the  very  existence  of  this  world,  depend  upon  the  con- 
stant but  unobserved  activity  of  three  invisible  and  in- 
tangible substances,  oxygen,  hydrogen,  and  nitrogen! 

QUESTIONS    ON    CHAPTER    6. 

1.  How  can  you  prove  the  presence  of  oxygen  in 
the  air? 

2.  What  prevents  the  immediate  destruction  of  the 
world  by  fire  ? 

3.  How  can  the  elements  mingled  in  air  be  separated  > 


76  THE   WORLD  OF  MATTER. 

4.  Describe  nitrogen. 

5.  What  is  ammonia? 

6.  What  is  the  meaning  of  the  word,  nitrogen? 

7.  What  are  the  uses  of  niter? 

8.  How  may  nitric  acid  be  produced? 

9.  What  are  its  effects  and  uses? 

10.  What  is  gun-cotton?     Its  advantages? 

U.  What  is  laughing  gas? 

12.  The  value  of  nitrogen  in  food? 


EARTH,  77 


CHAPTER  VII. 

EARTH. 

We  have  learned  that  the  old  notion  that  water,  air, 
and  fire  are  elementary  substances,  is  incorrect.  It  is 
hardly  necessary  to  add  that  those  who  held  this  opinion 
were  equally  wrong  in  thinking  that  "earth"  was  a 
fourth  and  final  element,  if  by  "earth"  they  meant 
what  is  now  commonly  understood,  namely,  the  soil 
under  our  feet,  for  I  have  already  told  you  that  about 
one-half  of  this  consists  of  oxygen  in  combination 
with  other  substances,  and  that  hydrogen  and  nitrogen 
are  also  found  in  it  in  vast  quantities. 

Before  going  on  to  study  the  form  of  earth  known 
as  soil,  it  is  only  fair  to  the  ancient  philosophers  from 
whose  writings  this  popular  theory  of  the  "four  ele- 
ments" took  its  rise,  to  say  that  the)''  never  meant  any- 
thing of  the  sort.  They  were  quite  intelligent  gentle- 
men, and  knew  as  well  as  we  know,  that  there  are  more 
than  four  different  substances  in  nature;  or  at  all  events 
more  than  four  apparently  different  substances.  What 
they  intended  to  say  was  more  nearly  this,  that  all  the 
elements  of  the  world  exist  in  four  different  states  or 
conditions;  namely,  solid,  liquid,  gaseous,  and  a  fourth 
state  still  further  removed  from  the  solid  form — a  state  in 
which  matter  still  more  rarefied  surrounds  and  interpene- 


78  THE  WORLD   OF  MATTER. 

trates  all  the  grosser  forms.  This  closely  resembles  that 
subtle  and  almost  hypothetical  form  of  matter  which 
modern  philosophers  believe  to  pervade  the  earth,  and 
the  remote  spaces  beyond  the  air,  and  which  they  call 
"the  ether."  I  do  not  say  that  the  ancients  had  as 
clear  and  scientific  a  knowledge  of  the  stuff  the  earth 
is  made  of  as  modern  students  have,  but  the  words, 
"solid,"  "liquid,"  "gas,"  and  "ether,"  are  much  more 
accurate  interpretations  of  their  classic  formulas,  than  the 
popular  but  misleading  words,  "earth,"  "water,"  "air," 
and  "fire." 

Let  us  now  examine  a  handful  of  earth  from  the 
garden,  not  attempting  to  discover,  perhaps,  all  its  ele- 
ments, but  carefully  enough  to  satisfy  ourselves  that  it 
is  composed  of  several  different  substances. 

I  have  here  a  little  earth  in  a  saucer.  It  is  a  dark- 
brown  substance,  resembling,  but  for  color,  some  of  the 
cheaper  grades  of  brown  sugar.  There  are  little 
grains  in  it,  with  here  and  there  small  lumps  which 
crumble  easily  at  a  touch.  Bits  of  straw  and  tiny  root- 
fibers  can  be  seen  without  close  observation.  These 
evidently  come  from  the  fertilizer  which  was  spread 
over  the  garden  last  fall,  and  plowed  in  this  spring. 

1  will  now  put  some  of  the  earth  under  a  microscope. 
Using  at  first  a  hand-lens  of  low  power,  it  seems  that 
this  earth  is  composed  of  tiny  grains  of  sand  of  different 
colors.  Some  are  black  and  dull,  some  white,  some 
transparent  and  glassy,  some  brown,  some  thin,  scale- 
like,  and  glistening.  It  is  a  curious  mixture,  I  now 
place  a  smaller  quantity  on  a  glass  slide,  and  examine  it 


fiARTH.  70 

under  a  more  powerful  lens.  It  is  at  once  transformed 
from  a  brown  powder  into  a  heap  of  tiny  pebbles  of 
various  colors,  shapes,  and  sizes.  Most  of  these  tiny 
pebbles  are  transparent,  and  of  a  brownish  tint;  many 
of  them  have  a  crystalline  appearance.  My  garden  is 
clearly  composed  mainly  of  a  fine  sand  or  loam.  The 
tiny  pebbles  under  the  glass  seem  to  be  mingled  with  a 
finer  and  smoother  substance  which  I  recognize  as  clay ; 
and  the  presence  of  minute  particles  of  vegetable  matter 
is  everywhere  more  visible  than  to  the  naked  eye. 

Let  me  now  heat  some  of  the  earth.  I  put  it  in  this 
test-tube,  and  hold  it  over  the  flame  of  an  alcohol  lamp. 
If  I  had  no  test-tube  I  should  put  it  on  a  shovel,  and 
cover  it  with  an  old  tumbler. 

The  first  thing  noticed  as  the  earth  grows  hot  is  a 
change  of  color.  It  is  becoming  lighter — at  the  same 
time  the  sides  of  the  tube  are  growing  foggy,  and  now 
drops  of  water  are  trickling  down  in  it.  A  quantity  of 
water  was  in  the  soil,  and  it  has  been  converted  into 
vapor  and  driven  off.  After  longer  heating  the  earth 
becomes  quite  dry,  and  now  there  appear  here  and 
there  little  sparks  and  small  glowing  coals,  that  flicker 
for  a  moment  and  go  out.  The  bits  of  straw  and  roots 
are  burning  up.  First  they  grow  very  hot,  and  give 
off  little  puffs  of  smoke  and  gas;  then  they  turn  black 
like  bits  of  charcoal;  then  when  still  hotter  they  com- 
bine with  oxygen  of  the  air  With  a  bright  red  glow,  and 
then  they  crumble  down  into  gray  ashes.  I  now  put 
the  earth  in  the  test-tube  between  two  pieces  of  glass, 
press  them  tightly  together,  and  slip  the  upper  one 


8o  THE  WORLD  OF  MATTER. 

along  over  the  earth.  I  hear  a  grating  sound,  and  on 
examining  the  glass,  I  find  that  it  is  covered  with  dis- 
tinct scratches. 

So  I  might  go  on  and  make  many  other  interesting 
experiments  with  this  handful  of  garden-soil,  but 
enough  has  been  done  for  our  present  purpose.  We 
have  learned  beyond  question  that  earth  is  not  an  ele- 
ment, but  a  mixture  of  many  different  substances. 

We  have  found  oxygen  and  hydrogen  in  the  water 
driven  off,  carbon  in  the  charred  bits  of  straw  and 
roots,  clay  binding  together  the  little  grains  of  sand, 
and  these  sand-grains  themselves  of  various  sorts,  some 
soft  and  smooth,  others  hard  enough  to  scratch  a  pane 
of  glass.  It  is  plain  enough  that  these  bits  of  charcoal 
are  not  essentially  different  from  the  larger  pieces  on  the 
hearth;  that  these  minute  particles  of  clay  are  just  like 
the  large  masses  which  we  find  in  olay-beds;  and  that 
these  tiny  pebbles  which  constitute  the  sand  are  differ- 
ent only  in  size  from  the  larger  pebbles  found  in  general. 
It  will  be  more  convenient  to  study  them  in  their  larger 
forms  and  separately,  and  so  we  may  now  throw  away 
our  earth,  and  examine  the  substances  of  which  it  is 
composed  as  we  find  them  in  larger  specimens.  We 
will  begin  with  the  hard  stone  that  scratches  glass. 

In  the  collection  accompanying  this  book  you  will 
find  a  specimen  of  it,  No.  18.  It  is  apiece  of  quartz. 
Observe  first  its  physical  properties,  and  I  shall  ask 
you  to  determine  for  yourself  its  degree  of  hardness, 
specific  gravity,  lustre,  color,  and  streak,  and  its  fusi- 
bility. Test  it  also  to  discover  whether  it  is  brittle  or 


EARTH.  81 

O~  £  J.  \  *i-  ••';;'..> 

not.  When  you  break  it  for  this  purpose,  observe 
whether  it  splits  evenly  as  a  piece  of  slate  does,  or 
whether  the  surfaces  after,  breaking  are  irregular.  The 
manner  in  which  a  mineral  breaks  is  often  important  as 
indicating  its  structure,  and  therefore  as  a  step  toward 
identifying  it.  The  peculiar  breaking  of  a  mineral  is 
called  its  fracture.  If  it  splits  more  or  less  evenly, 
such  splitting  is  called  cleavage,  instead  of  fracture. 

Drop  a  little  hydrochloric  acid  from  the  end  of  a 
glass  rod  upon  the  specimen.  What  effect  does  it  have? 

Specimen  No.  19  is  a  crystal  of  quartz.  You  will 
observe  that  it  is  six-sided,  or  hexagonal,  and  if  it  has 
not  been  broken,  it  is  also  finished  at  one  or  both  ends 
with  an  hexagonal  pyramid.  These  crystals  may  be 
found  in  almost  every  part  of  the  world,  for  a  large 
part  of  the  solid  crust  of  the  earth  is  composed  of 
quartz.  They  are  often  found  loosely  scattered  in  sand, 
which  is  formed  by  crumbled  or  "disintegrated"  rock, 
but  they  naturally  occur  in  veins  which  run  through 
other  sorts  of  rock. 

Quartz  crystals  were  believed  by  the  ancients  to  be 
merely  a  kind  of  ice  frozen  too  hard  to  melt;  but  they 
are  now  known  to  result  from  a  solution  of  the  mineral 
in  water,  which  trickling  through  crevices  in  the  rock 
gradually  evaporates,  and  slowly  builds  up  the  crystals 
from  the  quartz  dissolved  in  it.  The  name  "crystal,"  a 
Greek  word  for  ice,  is  still  retained  as  a  result  of  the  old 
and  erroneous  opinion.  Nothing  can  be  more  delight- 
ful than  the  finding  of  a  crystal  vein;  it  repays  many 
days  of  searching.  Some  years  ago  one  of  my  pupils 
6 


§2  THE  WORLD   OF  MATTER. 

in  Lenox  Academy  discovered  a  few  loose  crystals  of 
quartz  remarkable  for  their  brilliancy  and  symmetrical 
form.  It  was  suggested  that  as  these  had  been  found 
in  a  regular  line  along  the  crumbling  edge  of  a  rock,  a 
little  digging  might  reveal  a  vein;  and  the  boys  were 
invited  to  meet  in  the  field  at  a  certain  hour  prepared  to 
"stake  out  their  claims,"  and  enter  upon  a  small  mining 
operation.  The  appointed  hour  brought  a  most  amus- 
ing scene.  One  boy  had  a  large  hammer  and  a  drill ; 
another  a  shovel  and  an  old  iron  spoon;  another  a  crow- 
bar and  a  garden  trowel;  another  a  post-hole  digger 
that  opened  and  shut  like  a  huge  pair  of  shears;  while 
one  excited  youth  appeared  with  a  can  of  powder  and 
a  fuse.  Little  labor,  however,  was  needed.  A  few 
strokes  of  the  shovel  removed  a  layer  of  earth,  and  a 
cry  of  pleasure  arose  from  all  the  group.  A  narrow 
crevice  in  the  limestone  rock  was  revealed,  and  it  was 
filled  from  end  to  end  with  gleaming  crystals  of  trans- 
parent quartz ;  some  loose,  others  united  in  groups  and 
clusters  of  great  beauty;  and  ranging  from  the  size  of 
a  pea  to  that  of  a  butternut.  Some  were  tinged  with 
yellow,  others  clear  as  water.  Some  were  nearly  regu- 
lar in  form,  but  most  of  them  were  curiously  distorted, 
yet  every  one  was  hexagonal,  every  angle  measured  the 
same  number  of  degrees  as  every  other,  and  each  had 
on  one  end,  at  least,  a  pointed  pyramid. 

Down  dropped  the  little  miners  on  hands  and  knees, 
regardless  of  torn  trousers  and  finger-nails.  When  the 
sun  went  down  all  were  still  at  work,  with  their  earth- 
stained  heads  all  down  out  of  sight,  and  their  heels  all 


EARTtt.  83 

up  in  the  air;  and  every  boy  learned  more  about  quartz 
in  that  short  summer  afternoon  than  he  could  have  dug 
out  of  books  in  a  month.  So  can  you  if  you  will  follow 
their  example,  and  make  a  careful  examination  of  the 
country  within  ten  miles  of  your  own  home.  You  may 
not  find  a  vein  of  crystals,  but  you  will  find  plenty  of 
interesting  mineral  specimens  of  some  sort  to  repay 
you  for  your  pains.  You  should  make  a  mineralogical 
map  of  your  town,  upon  which  you  will  indicate  the 
location  of  the  various  minerals  you  find;  and  you 
should  make  a  collection  of  all  local  minerals,  labelling 
each  specimen  carefully,  and  being  particular  to  add  the 
exact  place  from  which  it  was  taken. 

Possibly  one  reason  that  quartz  so  closely  resembles 
ice  is  that  more  than  half  of  it  is  composed  of  the 
principal  element  of  water;  namely,  oxygen. 

The  other  element  in  quartz  is  new  to  you ;  it  is  called 
silicon,  and  is  never  found  in  nature  except  in  combina- 
tion with  oxygen,  from  which  it  is,  however,  extremely 
difficult  to  separate  it.  In  spite  of  this  difficulty,  how- 
ever, it  is  so  important  for  you  to  get  acquainted  with  the 
element,  since  next  to  oxygen  it  is  the  most  abundant  in 
the  world,  that  I  will  tell  you  how  the  chemist  Berzelius 
obtained  pure  silicon  in  1823. 

He  took  advantage  of  the  well-known  preference  of 
fluorine  for  metallic  over  non-metallic  substances,  on  the 
same  principle  by  which  we  obtained  hydrogen  when 
we  passed  steam  over  red-hot  iron.  You  'remember 
.that  in  that  case  the  oxygen  left  the  hydrogen  and  united 
with  the  iron. 


84  THE  WORLD  OF  MATTER. 

Berzelius  put  ten  parts  of  dry  potassium  silicon  fluor- 
ide— a  compound  of  the  metal  potassium  with  silicon, 
and  a  gas  called  fluorine — into  an  iron  tube;  his  object 
being  to  induce  the  fluorine  and  potassium  to  leave  the 
silicon:  he  then  added  nine  parts  of  metallic  potassium, 
and  heated  the  mixture  red-hot.  This  produced  a 
violent  commotion  among  the  elements  in  the  tube,  and 
when  it  was  all  over,  and  the  tube  cooled  down,  he 
found,  as  he  had  hoped,  that  the  charms  of  the  metallic 
potassium  had  proved  strong  enough  to  overcome  even 
the  attachment  which  had  previously  existed  between 
the  fluorine  and  the  silicon.  The  fluorine  and  potassium 
were  united  together  in  a  new  compound— potassium 
fluoride — and  the  deserted  silicon  was  left  alone. 

Before  Berzelius  got  hold  of  it,  however,  he  had  to 
shake  up  the- whole  mixture,  first  in  cold  and  then  in 
hot  water,  to  dissolve  out  the  potassium  fluoride.  When 
this  was  done,  he  found  the  pure  silicon  settled  at  the 
bottom,  and  on  taking  it  out  and  drying  it,  he  had  a 
brown  powder,  and  was  perhaps  the  first  human  being 
to  see  and  handle  this  wonderful  and  most  important 
element.  I  do  not  know  why  you  may  not  succeed  in 
repeating  his  experiment  and  sharing  his  delight. 

On  experimenting  with  this  silicon  powder,  it  was 
found  that  neither  sulphuric  nor  nitric  acid  affected  it; 
but  when  heated  in  the  air  it  readily  entered  into  com- 
bustion with  oxygen,  forming  an  artificial  quartz, 
which  often  melted  around  particles  of  the  silicon 
powder,  leaving  a  portion  of  it  unburned  in  the  centre. 

When   minerals  occur  in  an    uncrystallized    state,  as 


EARTH.  85 

when  carbon  is  in  the  form  of  charcoal,  or  silicon  in 
the  form  of  this  brown  powder,  they  are  called 
"amorphous" — which  simply  means  without  definite 
form. 

By  other  processes  silicon  has  been  obtained  in  dark 
and  glittering  eight-sided  crystals,  and  also  in  regular 
double  six-sided  pyramids,  of  a  dark  steel-gray  color. 
It  is  not  a  metal. 

QUESTIONS    ON    CHAPTER    7. 

1.  Is  "earth"  an  element? 

2.  What  did  the  ancient  philosophers  mean  by  speak- 
ing of  the  "four  elements,  fire,  water,  earth,  and  air?" 

3.  Describe   the  results  of  your   examination  of  a 
handful  of  garden  soil. 

4.  What  substances  are  most  abundant  in  it? 

5.  Describe  the  physical  properties  of  quartz. 

6.  Of  what  two  elements  is  quartz  composed? 

7.  What   then  is   its   chemical    name?     (Oxide  of 
silicon.) 

8.  Describe  a  crystal  of  quartz. 

9.  How  are  quartz  crystals  formed  ? 
10.     Describe  silicon. 


86  THE   WORLD   OF  MATTER. 


CHAPTER  VIII. 

QUARTZ. 

In  the  previous  chapter,  by  an  examination  of  a  hand- 
ful of  loam  we  learned  that  earth  is  not  one  element, 
but  a  mixture  of  many  minerals,  chief  among  which  is 
quartz.  \Ve  further  learned  the  more  prominent  physi- 
cal properties  of  quartz,  and  its  chemical  composition. 

How  large  masses  of  quartz  rock  are  split  by  frost, 
broken  down  and  rounded  into  pebbles  by  the  action  of 
weather  and  water,  and  at  last  reduced  to  fine  sand,  will 
be  more  fully  explained  in  the  third  volume  of  this 
series,  where  we  hope  to  treat  somewhat  in  detail  of  the 
forces  which  are  constantly  at  work,  changing  the  form 
and  modifying  the  structure  of  the  earth's  crust;  but  as 
this  mineral  constitutes  a  very  large  part  of  this  crust, 
we  shall  be  justified  in  devoting  a  few  more  pages  to  it 
now. 

No  mineral  appears  in  more  numerous  and  varied 
forms  than  quartz.  We  have  seen  it  in  its  transparent 
forms  as  a  fragment  of  rock,  and  as  a  gleaming  crystal. 
In  these  forms  it  rivals  in  transparency  the  finest 
glass.  From  it  spectacles  are  sometimes  made,  and  for 
this  purpose  Brazil  furnishes  some  of  the  finest  pebbles; 
but  it  is  doubtful  whether  it  posesses  any  real  advan- 
tage over  glass,  except  that  being  much  harder  it  is  less 


QUARTZ.  87 

likely  to  be  scratched.  The  ancients  made  exquisite 
goblets,  cups,  vases,  and  seals  of  rock-crystal.  Mr. 
Ruskin  pronounces  a  perfect  sphere  of  rock-crystal  one 
of  the  most  beautiful  objects  in  the  world.  These  are 
made  in  Japan,  sometimes  five  or  six  inches  in  diameter 
an"d  costing  hundreds  of  dollars.  In  their  perfect  clear- 
ness and  perfect  shape  they  rival  the  transient  glory  of 
soap-bubbles,  while  their  hardness  and  exquisite  polish 
render  them  almost  indestructible. 

One  of  the  common  varieties  of  quartz  is  flint.  It  is 
from  silex,  the  Latin  name  for  flint,  that  the  name 
silicon  is  derived.  Flint  varies  in  color  from  nearly  black 
to  light  brown,  red,  yellow,  and  grayish  white,  and  is 
sometimes  veined,  clouded,  marbled,  or  spotted.  It 
breaks  with  a  curved  fracture,  called  "conchoidal,"  or 
shell-like,  and  is  translucent.  Its  coloring  is  due  to  the 
presence  in  minute  quantities  of  other  substances,  such 
as  lime,  iron,  and  carbon.  It  is  abundantly  found  in 
beds  of  chalk.  Its  property  of  striking  fire  with  steel 
is  well  known,  and  before  the  invention  of  friction- 
matches  led  to  the  general  use  of  flint  for  kindling  fires 
and  firing  guns.  Old  "flint-lock"  muskets  and  pistols 
are  still  preserved  in  historical  museums. 

Sparks  may  be  struck  by  steel  from  any  hard  mineral, 
but  flint  sparks  are  so  hot  and  brilliant  that  it  is  thought 
that  they  are  due  not  only  to  particles  of  the  stone 
heated  to  redness  by  friction,  but  that  a  chemical  com- 
bination of  silica  {silicon  dioxide)  and  iron  takes  place. 
•  The  most  ancient  use  of  flint  was  probably  for  sharp 
weapons  and  cutting-tools.  Flint  knives,  axes,  and 


88  THE  WORLD  OF  MATTER. 

arrow-heads  are  among  the  most  interesting  relics  of  the 
Indians  and  other  savage  peoples.  The  principal  use 
of  flint  at  present  is  in  the  manufacture  of  fine  earthen- 
ware, and  particularly  in  the  preparation  of  the 
delicate  glaze  or  enamel  which  covers,  protects,  and 
adorns  it. 

An  interesting  natural  form  of  quartz  is  the  geode. 
Geodes  are  approximately  round  shells  of  rock,  lined 
with  crystals,  or  with  minerals  in  distinct  layers.  They 
range  in  diameter  from  a  quarter  of  an  inch  to  a  foot  or 
more.  When  water  holding  a  mineral  in  solution  finds 
its  way  into  a  hollow,  and  deposits  the  mineral  there  in 
layers  or  in  crystals,  a  geode  is  formed.  If  the  mineral 
in  solution  is  silica,  quartz  crystals  may  result.  If  the 
quartz  is  deposited  in  layers,  these  usually  appear  with 
different  shades  of  color,  and  such  variegated  layers  of 
quartz  are  known  as  agate.  If  the  color  of  the  quartz 
remains  uniform,  and  particularly  if  it  is  deposited  in 
curved  forms  like  clusters  of  grapes,  and  of  a  waxy 
lustre,  it  is  called  chalcedony.  If  the  color  is  red,  we 
have  a  geode  of  carnelian,  sard,  or  sardius. 

The  question  naturally  arises,  how  the  cavities  in 
which  these  crystals  and  layers  occur  are  formed. 
One  way  is  by  the  production  of  steam  inside  the 
rock  material  while  that  is  in  a  soft  or  "plastic"  state ; 
as  is  seen  in  the  sponge-like  slag  or  scoria  of  a  furnace 
or  a  volcano.  Rocks  which  were  once  in  a  melted  con- 
dition, like  the  "trap-rock"  of  the  Palisades  along  the 
Hudson  river,  afford  some  of  the  most  beautiful  geodes. 
Another  method  by  which  the  cavities  may  be  made,  is 


QUARTZ.  89 

by  the  dissolving  action  of  water  on  fossils.  The  sol- 
vent water  eats  out  the  fossil  shell  or  coral. 

Perhaps  a  clergyman  might  find  a  sermon  in  these 
stones.  The  hidden  crystals  must  remain  entirely  lustre- 
less until  the  geode  is  broken.  Though  they  have  the 
power  of  shining  so  brilliantly,  they  come  to  their  glory 
only  when  shattered.  In  losing  their  life  they  find  it. 

Onyx  and  sardonyx  are  varieties  of  agate,  in  the  first 
of  which  the  alternate  layers  are  white  and  dark  brown 
or  black;  and  in  the  second,  reddish  yellow  or  orange. 

Moss-agates,  or  mocha-stones,  are  formed  by  the  in- 
fusion of  a  solution  of  manganese  or  some  other  mineral 
into  the  quartz,  where  it  often  closely  imitates  the 
branchings  of  moss  or  little  fibers  of  root.  It  is  possible 
that  these  forms  may  in  rare  instances  be  due  to  actual 
fibers  or  sprays  of  moss,  which  were  once  imbedded  in 
the  quartz,  and  dissolved  out  by  the  water;  in  which 
case  they  may  be  considered  as  tiny  geodes. 

Prase,  or  chrysoprase,  is  a  beautiful  pea-green  variety 
of  quartz,  and  is  often  found  in  alternate  layers  with 
white  chalcedony. 

One  of  the  handsomest  varieties  of  quartz  is  amethyst, 
which  by  the  oxide  of  manganese  or  iron  is  tinged  with 
brilliant  purple.  The  name  "amethyst"  means  "a  pre- 
venter of  intoxication,"  and  was  given  to  this  mineral 
by  the  Greeks,  who  believed  that  from  a  cup  of  amethyst 
one  could  drink  wine  and  escape  a  headache.  Fine 
specimens  are  found  in  Lincoln  County,  North  Carolina, 
on  the  shores  of  Lake  Superior,  and  in  Colorado.  The 
finest  varieties  are  from  Brazil,  Ceylon,  India,  and  Siberia. 


90  THE   WORLD   OF  MATTER. 

The  inspired  St.  John  is  largely  indebted  to  quartz 
for  his  conception,  of  the  glory  of  the  New  Jerusalem : 
"The  building  of  the  wall  thereof  was  jasper:  The 
first  foundation  was  jasper;  .the  third  chalcedony;  the 
fifth  sardonyx;  the  sixth  sardius;  the  tenth  chrysoprase; 
the  twelfth  amethyst."  Surely  a  mineral  which  not 
only  composes  much  of  the  crust  of  the  present  earth 
but  which  is  also  to  be  found  in  such  abundance  in  the 
foundations  of  the  "New  Earth"  that  is  to  be,  deserves 
our  careful  study ! 

Another  beautiful  compound  of  silicon  must  be  men- 
tioned here,  which  differs  in  composition  from  quartz 
only  in  containing  from  5  to  13  per  cent,  of  water, 
although,  as  with  quartz,  iron,  and  other  substances  fre- 
quently give  it  a  tinge  of  color.  This  is  opal.  It  is 
never  found  crystallized.  It  has  a  conchoidal  or  shell- 
like  fracture  like  chalcedony,  and  is  very  brittle.  The 
finest  variety  is  called  "precious"  or  "noble,"  or  "orien- 
tal" opal.  It  is  translucent,  of  a  bluish  or  yellowish 
hue,  and  exhibits  a  beautiful  play  of  rainbow  tints.  The 
finest  opals  come  from  Hungary.  Common  opal  is  less 
clear,  and  does  not  have  any  play  of  color.  Wood- 
opal  is  a  petrifaction  retaining  the  form  and  apparent 
structure  of  the  wood  which  has  been  dissolved  away, 
and  replaced  by  the  silicious  mineral. 

Three  beautiful  varieties  of  common  rock-crystal  re- 
main: milky-quartz, which  is  opaque  and  white  as  snow; 
rose-quartz,  which  is  transparent  and  of  the  most  deli- 
cate rose-color;  and  smoky-quartz,  which  is  translucent 
and  tinged  with  grayish  brown.  It  will  be  well  to 


QUARTZ.  91 

notice  that  all  varieties  of  quartz  fall  naturally  into  two 
groups:  (i)'the  clear,  glassy  kinds,  like  rock-crystal, 
amethyst,  rose-quartz,  and  the  like,  and  (2)  the  waxy 
or  dull  kinds,  such  as  chalcedony,  agate,  and  flint. 

Quartz  constitutes  nearly  all  the  sand  of  the  sea-shore, 
and  of  the  great  deserts.  The  small  particles  of  mo^t 
other  minerals  are  dissolved  by  water,  while  those  of 
quartz  remain  hard  and  "shaip." 

Of  the  numerous  uses  of  sand,  I  mention  five.  You 
are  perfectly  familiar  with  its  use  on  sand-paper,  and  as 
a  covering  for  "silicate"  slates,  and  blackboards. 

In  1870,  Benjamin  Tilghman,  of  Philadelphia,  in- 
vented the  "sand-blast,"  a  rapid  stream  of  sharp  sand 
driven  against  glass,  stone,  or  metal,  for  the  purpose  of 
cutting,  boring,  or  engraving.  By  its  use,  also,  blocks 
of  stone  may  be  turned  in  a  lathe  into  circular  and  other 
forms.  Pilasters  have  in  this  way  been  finished  in  a  few 
hours,  while  if  cut  by  hand  as  many  days  would  have 
been  needed. 

Sand  is  one  of  the  chief  ingredients  in  plaster  and 
mortar,  being  united  with  lime  to  form  a  strong  and 
durable  cement. 

Its  chief  use,  however,  is  in  the  manufacture  of  glass, 
which  is  composed  of  quartz,  united  with  iime,  soda, 
metallic  oxides,  or  other  substances. 

There  is  a  legend  that  glass  was  accidentally  discov- 
ered ages  ago,  by  certain  Phoenician  merchants,  who 
were  returning  home  in  a  ship  laden  with  soda,  and 
who  were  compelled  by  a  storm  to  land  on  a  sandy 
shore  under  Mt.  Carmel.  They  propped  up  their  cook- 


92  THE   WORLD   OF  MATTER. 

ing-pots  by  lumps  of  soda  placed  on  the  sand,  and 
when  these  and  the  sand  were  melted  by- their  fires  the 
first  glass  was  formed ;  but  this  is  not  the  place  to  enter 
into  a  history  or  description  of  glass-making,  nor  even 
to  enumerate  the  most  important  of  its  countless  uses. 

Although  quartz  is  so  useful  in  the  construction  of 
our  dwellings  in  the  form  of  sand  for  mortar,  it  is  no 
less  valuable  when  naturally  compacted  and  mingled  in 
various  forms  of  building-stone.  All  our  sandstone, 
for  example,  is  largely  composed  of  quartz,  and  quartz 
is  one  of  the  necessary  ingredients  of  granite,  gneiss, 
and  many  other  r.ocks. 

Finally,  quartz  or  silica  occurs  in  many  vegetable 
structures,  giving  them  strength  and  hardness,  and  often, 
as  in  the  case  of  stalks  of  grain,  a  fine  enameled  surface. 
It  also  occurs  in  sponges  in  little  needle  like  "spicules." 

Consider  th»  incalculable  evil  that  would  result  from 
the  sudden  destruction  of  the  silicon  that  is  in  the  world ! 
The  contents  of  every  glass  tumbler  and  jar  and  bottle, 
would  be  let  loose;  microscopes  and  telescopes  and 
spectroscopes  would  vanish.  Rain  and  wind  would 
have  free  access  to  our  homes  through  empty  window 
frames;  stone  and  brick  buildings  would  crumble  to  the 
ground;  mountains  and  the  solid  crust  of  the  earth 
would  sink  away,  and  the  oxygen  now  safely  held  in 
the  strong  grasp  of  silicon  would  be  let  loose  to  consume 
the  whole  world  with  fire. 

In  closing  this  chapter,  I  must  remind  you  that  in  using 
the  expression  "crust  of  the  earth,"  I  do  not  ,mean  the 
whole  mass  of  the  earth,  but  only  an  outer  shell,  a  few 


QUARTZ.  93 

miles  thick;  no  thicker  in  proportion  to  the  whole  earth 
than  the  varnish  on  a  school-globe.  Geologists  know 
nothing  by  personal  observation  about  the  materials 
of  which  the  great  bulk  of  the  earth  is  composed. 
They  have  only  scratched  around  a  little  here  and  there 
on  top.  There  are  reasons  known  to  astronomers,  how- 
ever, and  others  understood  by  electricians,  which  make 
it  not  incredible  that  the  earth  is  a  solid,  or  nearly  solid, 
mass  of  iron,  covered  over  with  a  layer  or  a  few  thin 
layers  of  various  sorts  of  rock,  and  topped  with  a  sprink- 
ling of  pulverized  rock,  called  earth  or  soil,  which  is 
altogether  too  thin  and  scanty  t"o  be  taken  largely  into 
account. 

QUESTIONS  ON  CHAPTER    8. 

1.  Describe  the  appearance  and  uses  of  rock-crystal. 

2.  Derivation  and  meaning  of  the  words  crystal  and 
silicon? 

3.  Describe  flint,  and  tell  its  uses. 

4.  What  are  geodes,  and  how  are  they  formed? 

5.  Describe  agate,  sardonyx,  and  onyx. 

6.  How  are  "moss-agates"  formed? 

7.  Describe  prase,  amethyst,  and  opal. 

8.  Uses  of  sand? 

9.  If    you    have  seen    glass  manufactured,  describe 
the  process. 

10.     What  results  would  follow  the    sudden    removal 
of  silicon  from  the  earth? 
n.     What  is  meant  by  the  "crust"  of  the  earth? 


94  THE   WORLD   OF  MATTER. 


CHAPTER  IX. 

A    LESSON    IN    CHEMISTRY. 

It  is  evident  from  what  we  have  now  learned  that 
changes  are  constantly  taking  place  in  mineral  sub- 
stances. We  have  seen  ice  changing  to  water,  and 
water  to  steam.  We  have  seen  iron  bursting  into  bril- 
liant flame  in  oxygen,  and  changing  into  iron  oxide. 
We  have  seen  water  changing  into  two  gases,  and  these 
gases  changing  back  again  into  water.  We  have  seen 
various  solutions  changing  into  vapor  and  crystals. 
Thinking  over  all  these  changes  you  will  see  that  they 
may  be  divided  into  two  classes: 

1.  Those  that  do  not  alter   the    composition  of  sub- 
stances. 

2.  Those  that  alter  the  composition  of  substances. 
Changes  of  the  first  kind  are  called  physical  changes. 

Those  of  the  second  kind  are  called  chemical  changes. 

The  change  from  water  to  ice  is  a  physical  change. 

The  change  from  water  to  oxygen  and  hydrogen,  or 
the  reverse,  is  a  chemical  change. 

From  the  experiments  we  have  made,  we  have  also 
learned  that  chemical  changes  may  be  caused:  (i).  By 
heat, or  electricity.  (2).  By  bringing  different  substances 
into  contact.  (3).  By  bringing  different  substances  to- 
gether in  a  solution. 


A   LESSON   IN   CHEMISTRY.  95 

In  all  cases  of  chemical  action,  we  have  observed  that 
the  substances  acted  upon  lose  their  distinctive  proper- 
ties, and  that  new  substances  with  different  properties 
are  formed. 

Notice  now  that  all  cases  of  chemical  action  may  be 
divided  into  three  classes:  (i)  Composition;  (2) 
Decomposition;  (3)  Double  decomposition. 

Double  decomposition  occurs  when  substances  act 
upon  one  another  and  give  rise  to  two  or  more  new 
substances  instead  of  one.  A  good  example  of  double 
decomposition  was  shown  in  the  process  by  which 
Berzelius  separated  silicon  from  potassium  silico-fluoride, 
page  83. 

What  it  is  that  causes  substances  to  combine  with 
one  another  is  not  known.  To  the  unknown  cause  of 
their  combination,  the  name  chemical  attraction  has 
been  given.  We  must  now  study  carefully  the  pro- 
portions in  which  the  different  elements  combine. 

Two  facts  have  been  .learned  by  experiment: 

1 .  The  same  chemical  compound  always  contains  the* 
same  elements  in  the  same  proportion  by  weight. 

Water,  for  example,  always  contains  the  same  ele- 
ments, oxygen  and  hydrogen,  and  in  the  same  propor- 
tion by  weight,  namely,  16  to  2.  This  is  called  the 
la^v  of  definite  proportions.* 

2.  The  proportionate  weight   of  each  element    in 
every  compound  is   always   expressed  by   a  particular 
number,  or  by  a  multiple  of  that  number. 

*  Recent  experiments  by  Professor  Edward  Morley  indicate  that  the  exact 
proportionate  weight  of  oxygen  in  water  is  between  15.877  and  15.882. 


£6  ^HE   WORLD   (DF   MATTED. 

For  example,  the  proportionate  weight  of  oxygen  in 
every  compound  is  always  expressed  by  1 6,  or  by  some 
multiple  of  160 

This  is  the  law  of  multiple  proportions. 

These  facts  can  be  explained  by  supposing  each  ele- 
ment to  be  made  up  of  little  particles  of  uniform  weight. 

For  illustration,  if  you  have  a  number  of  iron  balls, 
each  weighing  seven  ounces,  and  a  number  of  glass 
balls,  each  weighing  three  ounces,  it  is  plain  that,  how- 
ever you  may  mix  the  iron  balls  with  the  glass  balls, 
the  total  weight  of  glass  in  the  mixture  can  always  be 
expressed  by  three  or  some  multiple  of  three,  and  the 
total  weight  of  iron  by  seven  or  some  multiple  of  seven 

Now,  since  all  elements  combine  just  as  they  would 
if  they  were  made  up  of  particles  of  uniform 
weight,  chemists  assume  that  they  really  are  made 
up  of  such  particles;  and  since  these  particles  are  the 
smallest  possible  parts  into  which  an  element  can  be  di- 
vided, they  are  named  atoms,  a  Greek  word  meaning 
indivisible. 

It  is  believed  that  these  tiny  atqms  do  not  absolutely 
touch  one  another,  and  that  they  are  never  absolut'  ly 
at  rest.  If  a  mass  of  gold,  for  example,  could  be  viewed 
through  lenses  of  sufficient  power  to  reveal  its  structure, 
we  should  probably  see  as  wild,  and  apparently  con- 
fused, a  dance  of  atoms  as  that  of  the  motes  in  the  sun- 
beam, or  the  planets  in  the  sky.  I  say  "apparently" 
confused,  for  there  is  really  no  disorder  either  among 
the  atoms,  or  the  motes,  or  the  planets;  but  each  moves 
in  accordance  with  a  regular  and  well  defined  law. 


A   LESSON   IN   CHEMISTRY.  97 

Finally,  it  is  thought  these  atoms  occur  in  groups  of 
two  (or  in  some  elements  more,  but  a  constant  number 
for  each  element),  and  that  these  groups  are  never 
broken  up  except  when  the  element  enters  into  combi- 
nation with  some  other  substance.  These  Uttle  groups 
of  atoms  are  called  molecules,  a  word  meaning  simply 
"little  masses."  In  the  giddy  dance  of  atoms,  the  mole- 
cules move  together  like  inseparable  partners  in  a 
waltz. 

Molecules  of  a  single  element  may  be  called  simple 
molecules.  It  is  evident  that  the  smallest  particle,  or 
molecule,  of  a  compound  substance  must  be  made  up 
of  atoms  of  the  different  elements  of  which  it  is  com- 
posed. A  molecule  of  water,  for  instance,  is  made  up 
of  atoms  of  oxygen  and  hydrogen.  Such  molecules 
may  be  called  compound  molecules.  The  weight  of 
a  molecule  is  equal  to  the  sum  of  the  weights  of  the 
atoms  that  compose,  it. 

The  rapid  motion  of  atoms  and  molecules  to  which  I 
have  referred  is  closely  connected  with  the  phenom- 
ena of  heat.  The  hotter  they  are,  the  more  rapid  and 
extended  are  their  movements;  and  conversely,  the 
more  rapidly  the  molecules  are  made  to  move,  the 
hotter  they  grow. 

It  would  hardly  be  correct  to  say  that  heat  makes 
them  move,  or  that  their  motion  causes  heat;  it  would 
perhaps  be  better  to  say  that  their  motion  is  their  heat. 
At  all  events,  as  this  motion  or  heat,  or  both,  increases,  the 
substance  expands,  just  as  it  would  if  it  were  made  up  of 
little  masses  which  were  separating  farther  and  farther 
7 


98  THE   WORLD   OF  MATTER. 

from  one  another  and  getting  away  from  the  power  of 
one  another's  attraction.  As  the  heat  increases  the 
solid  passes .  into  the  liquid,  and  the  liquid  into  the 
gaseous  form.  In  the  gaseous  state  the  molecules  are 
no  longer  held  together,  but  are  violently  driven  farther 
and  farther  asunder. 

Avogadrtfs  Law:  In  1811,  a  chemist  named  Avo- 
gadro  announced  as  the  result  of  many  experiments  that 
equal  volumes  of  all  gases  under  the  same  conditions 
of  temperature  and  pressure  contain  the  same  number 
of  molecules. 

This  is  known  as  Avogadro's  law.  If  this  be  true, 
then  by  weighing  equal  volumes  of  gaseous  substances 
we  can  learn  the  relative  weights  of  the  molecules  of 
these  substances. 

From  the  molecular  weights  thus  determined,  the 
atomic  weights  of  the  elements  have  been  learned. 

As  hydrogen  enters  into  combination  in  smaller  pro- 
portion by  weight  than  any  other  element,  its  atomic 
weight  is  taken  as  the  unit.  When  we  say,  therefore, 
that  the  atomic  weight  of  oxygen  is  sixteen,  we  mean 
simply  that  one  atom  of  oxygen  is  sixteen  times  as 
heavy  as  one  atom  of  hydrogen. 

Chemical  symbols. — As  the  chemist  is  mainly  occu- 
pied in  studying  the  combination  of  atoms,  it  has  been 
found  convenient  to  represent  these  atoms  by  symbols, 
and  the  most  convenient  symbols  are  the  letters  which 
stand  for  the  names  of  the  elements.  Thus  the  letter 
O  is  used  to  represent  one  atom  of  oxygen,  the  letter 
H,  to  represent  one  atom  of  hydrogen,  etc.  When  the 


A   LESSON   IN   CHEMISTRY.  99 

names  of  several  elements  begin  with  the  same  letters, 
as  in  the  case  of  indium,  iodine,  and  indium,  a  seconu 
letter  is  added  to  distinguish  them;  thus  In  tor  maiurn, 
Ir  for  iridium;  and  when  this  is  not  practical,  as  in  tne 
case  of  iron,  where  I  or  lo  might  be  taken  for  iodine, 
Ir  for  iridium,  and  In  for  indium,  the  chief  letters  of 
their  Latin  names  are  used ;  thus,  Fe,  from  the  Latin 
"ferrum,"  iron,  is  the  symbol  for  that  element. 

The  student  should  now  carefully  examine  the  table 
of  elements  and  symbols  on  page  263.  It  is  not  best  to 
commit  them  to  memory  at  once.  They  will  gradually 
become  familiar  by  use.  The  numbers  after  the  sym- 
bols are  the  atomic  or  combining  weights  of  the  ele- 
ments. When  we  desire  to  express  the  fact  that  various 
elements  are  put  together,  we  write  their  symbols  one 
after  the  other  with  the  sign  (+)  plus  between  them. 
Thus  zH+O  means  that  two  atoms  of  hydrogen  are 
added  to  one  atom  of  oxygen.'  If  we  wish  to  express 
by  the  symbols  that  the  elements  thus  brought  together 
have  united  in  chemical  combination,  we  omit  the  sign 
+  and  write  the  symbols  closely  together  as  follows: 
H2O.  Such  an  expression  is  called  a  chemical  formula. 
Chemical  formulas  have  a  puzzling  look  to  the  be- 
ginner, but  they  are  really  of  the  greatest  use  both  in 
simplifying  our  language  and  in  rendering  chemical 
combinations  easy  to  understand. 

When  the  result  of  bringing  certain  elements  to- 
gether is  their  chemical  union,  we  express  that  fact  in 
the  following  form:  2H+O=H2O;  which  is  read: 
Two  atoms  of  hydrogen  added  to  one  atom  of  oxygen 


ioo  TtiE  WORLD  OF  MATTM. 

combine  to  form  water.  The  sign  of  equality  (=)  is 
very  convenient  here.  Such  a  formula  is  calle  J  a  chem- 
ical equation. 

As  the  symbols  of  the  elements  represent  atoms,  it  is 
evident  that  the  symbols  of  compounds  represent  mole- 
cules. The  symbol  for  water,  H2O,  represents,  accord- 
ing to  the  atomic  and  molecular  theories  already  ex- 
plained, the  smallest  particle  of  water  that  can  exist  as 
such.  It  is  made  up  of  two  atoms  of  hydrogen  and  one 
atom  of  oxygen,  chemically  combined. 

Exercise. — Read  the  following  equations: 

Hg-|-O=HgO  (Mercuric  oxide.) 

Na-f-Cl=NaCl  (Sodium  chloride  or  common  salt.) 

2N-j-2O=N8O8  (Nitric  oxide.) 

It  will  be  observed  that  before  combination  takes 
place  the  number  of  atoms  in  any  element  is  repre- 
sented by  a  large  figure  written  on  a  line  with  the  letters ; 
while  the  number  of  combined  atoms  is  represented  by 
a  small  figure  written  to  the  right  and  below  the  symbol 
to  which  it  belongs. 

In  laboratory  work  combinations  are  less  frequently 
made  between  two  elements  directly  than  between  com- 
pounds, and  it  is  in  expressing  completed  combinations, 
or  "reactions"  as  they  are  called,  that  the  value  of  sym- 
bols is  most  apparent. 

Recur  for  a  moment  to  the  experiment  by  which 
Berzelius  obtained  pure  silicon,  page  ^3.  Observe 
how  many  words  were  needed  to  explain  tne  comDina- 
tions  he  effected,  and  see  how  mucn  simpler  it  is  lo  ex- 
press the  same  reaction,  thus: 


A   LESSON   IN   CHEMISTRY.  101 

K2SiF6      -f          4K  6KF        -f          Si 

(Potassium-silicon     (Potassium.}       (Potassium         (Silicon.) 
fluoride.)  fluoride.) 

The  symbols  tell  the  whole  story  in  one  line;  not 
only  giving  us  the  substances  brought  together  and  the 
compounds  that  result,  but  also  the  exact  proportions 
of  each  by  weight. 

A  little  study  of  this  equation  will  show  you  that  the 
weight  of  the  resulting  substances  is  precisely  equal  to 
the  sum  of  the  weights  of  all  the  elements  that  are  com- 
bined. Turn  to  the  table  of  atomic  weights. 

The  atomic  weight  of  K  being  39.04,.  K8  =  78.08 
The  atomic  weight  of  Si  being  28,  Si  =  28.00 

The  atomic  weight  of  F  being  19.10,  F6  =  114.60 
The  atomic  weight  of  K  being  39.04,  4  K  =  156.16 
And  the  sum  is  .........................  376.84 

Now  add  the  weights  represented  in  the  other  side 
of  the  equation. 

The  weight  of  K  being   39.04,  an(*   the    weight 
of  F  being  19.10,  K  F  =  58.14;  and  6  K  F  =         348.84 
The  weight  of  Si  being  28,  Si=  28.00 

And  the  sum  is  again  ......................   376.84 

This  is  true  of  every  chemical  equation,  and  forcibly 
illustrates  a  fundamental  principle  of  the  science, 
namely,  that  nothing  is  ever  destroyed  by  any  chemi- 
cal process. 

Water  seems  to  boil  away,  but  every  molecuje  of  it 
continues  to  exist  in  the  form  of  vapor.  This  vapor 
may  be  decomposed  into  its  elemental  gases,  but  every 
atom  that  formerly  existed  in  the  water  is  still  pre- 


\       *        »*•        .  v 


102  THE   WORLD   OF   MATTER. 

served  in  the  gas.  Iron  was  burned  up  in  oxygen,  but 
both  were  found  in  their  full  weight  in  the  iron  oxide 
that  remained. 

As  no  element  is  ever  diminished  or  destroyed, 
so  no  elementary  substance  ever  increases  in  total 
quantity.  When  coal  is  burned  in  a  furnace,  the 
weight  of  the  vapor  and  smoke  that  escape  from  the 
chimney  is  about  four  times  as  great  as  that  of  the  coal 
consumed,  but  this  is  only  because  in  the  process  of  com- 
bustion nearly  three  tons  of  oxygen  have  combined  with 
every  ton  of  carbon. 

QUESTIONS    ON    CHAPTER    9. 

1.  Define  chemical  and  physical  changes. 

2.  State     three    methods    of    producing    chemical 
changes. 

3.  What  are  the  three  classes  of  chemical  changes? 

4.  What  causes  chemical  combination? 

5.  Give  the  laws  of  definite  and  multiple  propor- 
tions. 

6.  What  hypothesis  explains  them  ? 

7.  Distinguish  between  atoms  and  molecules. 

8.  What  is  Avogadro's  law? 

9.  What  is  the  unit  of  atomic  weight? 

10.  What  is  the  advantage  of  chemical  symbols? 

11.  Can  the  total  quantity    of   any   element  be    in. 
creased  or  diminished? 

12.  How  does  this  appear  in  chemical  equations? 


A  PIECE  OF  CHARCOAL.  103 


CHAPTER  X. 

A    PIECE    OF    CHARCOAL. 

Having  gone  out  of  our  way  in  the  last  chapter  to 
consider  some  of  the  laws  that  govern  the  elements  in 
their  chemical  combinations,  and  to  become  acquainted 
with  the  symbols  used  to.  express  those  combinations, 
or  "reactions,"  let  us  now  return  to  the  examination  of 
our  handful  of  earth. 

You  remember  that,  besides  a  quantity  of  water,  we 
had  already  found  in  it  a  large  number  of  minute 
grains  of  quartz,  composed  of  a  very  interesting  ele- 
ment, silicon,  in  combination  with  oxygen.  Notice,  in 
passing,  that  as  a  rule,  each  mineral  has  two  names,  one 
given  and  used  by  mineralogists,  as  in  this  instance 
quartz /  the  other  used  by  the  chemist  to  indicate  its 
composition,  as  silicon  oxide,  or  abbreviated,  SiO2. 

We  next  observed  bits  of  charcoal  scattered  through- 
out the  soil.  These  are  identical  in  substance  with  the 
large  pieces  of  charcoal  on  the  hearth,  and  consist  of  the 
element  known  as  carbon. 

Carbon  is  the  chief  element  in  the  composition  of  all 
the  substances  which  we  burn  for  the  sake  of  heat  or  light; 
including  wood,  coal,  gas,  oil,  tallow,  and  wax.  When- 
ever these  fuels  are  heated  to  redness  in  a  vessel  from 
which  air  is  excluded,  their  other  elements,  hydrogen 


104  THE   WORLD   OF  MATTER. 

and  oxygen,  are  first  driven  off  in  gaseous  forms,  partly 
as  water  and  partly  in  combination  with  carbon,  and  a 
large  portion  of  the  carbon  remains  behind,  mingled 
with  a  little  ash.  If,  now,  free  access  of  oxygen  be 
allowed,  the  carbon  combines  with  it  gradually,  not 
with  a  flame  but  with  a  steady  glow,  and  the  product  of 
this-  combustion  is  an  invisible  gas,  which  we  shall 
presently  study. 

The  purest  form  of  charcoal  is  lamp-black.  Char- 
coal does  not  crystallize,  and  is  therefore  an  amorphous 
form  of  carbon. 

You  are  so  familiar  with  the  physical  properties  of 
charcoal  that  you  need  not  devote  much  time  to  them 
now.  The  specific  gravity  of  this  substance,  however, 
is  greater  than  at  first  appears.  A  piece  of  charcoal 
floats  on  water,  and  appears,  thus  to  have  a  specific 
gravity  of  less  than  i ;  but  this  is  due  to  its  porous 
condition.  It  is  buoyed  up  by  the  air  which  fills  its 
pores.  If  it  be  finely  powdered  it  sinks  in  water,  and 
its  specific  gravity  is  found  to  range  from  1.5  to  2. 

Coke  is  a  form  of  carbon  made  by  heating  coal  with- 
out free  access  of  air,  as  is  done  on  a  large  scale  in  the 
manufacture  of  illuminating  gas.  Coke  bears  about 
the  same  relation  to  coal  that  charcoal  bears  to  wood. 

Lamp-black  is  a  very  finely  divided  form  of  charcoal, 
which  is  deposited  on  cool  objects  placed  in  the  flames 
of  burning  oils.  Most  artificial  lights  deposit  a  black 
soot  on  objects  placed  in  them. 

This  soot  is  used  in  the  manufacture  of  printer's  ink-. 

Carbon  is  acted  upon  by  very  few  substances,  and  i§ 


A   PIECE   OF  CHARCOAL.  105 

nearly  insoluble,  so  that  it  is  impossible  to  destroy  the 
color  of  printer's  ink  without  destroying  the  material 
upon  which  it  is  impressed. 

Bone-black,  or  animal  charcoal,  is  made  by  charring 
bones  or  other  animal  substances. 

Bone-black  and  wood  charcoal  have  the  power  of  ab- 
sorbing gases,  and  are  therefore  useful  as  purifiers  of 
foul  air.  Charcoal  also  absorbs  many  of  the  impurities 
contained  in  foul  water,  and  is  extensively  used  in 
filters.  A  charcoal  filter  should  be  of  good  size,  and 
the  charcoal  should  be  occasionally  renewed. 

Some  coloring  matters  are  removed  from  liquids  by 
passing  them  through  filters  of  bone-black.  This  is  of 
practical  advantage  in  the  refining  of  sugar.  The  syrup 
first  obtained  from  the  cane  or  beet  is  strongly  colored, 
but  the  color  is  removed  by  filtering  through  bone- 
black. 

Many  impure  varieties  of  amorphous  carbon  are  in- 
cluded under  the  name  coal.  They  all  bear  a  more  or- 
less  close  relation  to  charcoal,  and,  like  it,  have  been 
formed  by  the  gradual  decomposition  of  wood  or  other 
vegetable  material  without  free  access  of  air.  The  pro- 
cess has  been  going  on  for  ages.  It  will  be  more  fully 
treated  in  the  succeeding  volumes  of  this  series.  Ordi- 
nary coals  are  classed  as  hard  and  soft,  or  anthracite 
and  bituminous.  Then  there  are  substances  in  which 
the  decomposition  has  not  progressed  so  far,  such  as 
lignite  and  peat. 

I  must  call  your  attention  again,  and  particularly,  to 
the  fact  that  charcoal  unites  with  oxygen  without 


106  THE   WORLD    OF   MATTER. 

flame,  and  while  it  is  in  the  solid  state.  The  solid  par- 
ticles of  the  carbon  as  they  burn  with  the  oxygen  be- 
come glowing  white  or  incandescent,  and  thus  give  rise 
to  the  brightness  of  all  ordinary  flame.  If  it  were  not 
for  the  presence  of  incandescent  or  white-hot  particles 
of  carbon,  our  hearth-fires,  and  lamps,  and  candles,  and 
gas-jets  would  all  be  reduced  to  a  feeble  sort  of  flame, 
such  as  that  given  by  burning  alcohol.  This  follows  from 
a  very  important  principle,  namely,  that  whenever  a 
substance  burns — as  iron  burns  in  oxygen,  and  as  car- 
bon burns  in  Edison's  electric  lamp — without  first  as- 
suming the  vaporous  state,  it  becomes  exceedingly  lumi- 
nous. In  fact,  when  any  substance  is  intensely  heated 
it  becomes  intensely  bright,  whether  it  burns  or  not,  if 
it  retains  its  solid  state.  If  a  candle  or  lamp  does  not 
burn  well  it  gives  off  a  quantity  of  smoke.  This  is 
merely  unburned  carbon.  It  is  this  very  smoke  which 
gives  brilliance  to  the  light  if  it  does  burn  well.  In 
that  case  the  particles  of  smoke,  which  are  carbon,  be- 
come incandescent,  and  give  a  beautiful  light,  while  at 
the  same  time  they  combine  with  oxygen  in  the  form 
of  an  invisible  gas  and  pass  away  into  the  air.  You 
may  perform  a  simple  but  instructive  experiment  to 
illustrate  the  part  that  carbon  plays  in  giving  brilliancy 
to  flame. 

To  show  you  how  abundant  carbon  is,  and  how  it 
exists  in  places  where  you  would  perhaps  least  expect 
to  find  it,  we  will  procure  the  carbon  for  this  experiment 
from  a  lump  of  sugar.  Lay  a  piece  of  writing-paper 
on  a  fire-shovel,  place  a  lump  of  sugar  on  it,  and  hold 


A   PIECE   OF  CHARCOAL.  107 

it  over  glowing  coals.  Sugar  is  nothing  but  carbon  and 
water.  You  will  presently  see  the  sugar  melt;  then 
the  water  will  pass  off  in  the  form  of  vapor — which 
you  can  collect  and  examine — and  finally  you  have  left 
a  light,  porous,  cindery,  black  mass,  which  is  carbon  in 
the  form  of  charcoal.  Thus  far  we  have  merely  driven 
off  the  water  from  the  sugar  by  means  of  heat. 

We  might  have  separated  it  equally  well  by  mixing 
sugar  in  the  form  of  syrup  with  sulphuric  acid.  The 
acid  would  have  combined  with  the  water,  leaving  the 
carbon  in  a  black  mass. 

Now  fasten  a  little  splinter  of  wood  by  a  fine  wire  to 
your  mass  of  charcoal,  set  fire  to  the  wood  so  as  to  start 
the  combustion,  and  then  plunge  the  charcoal  into  a  jar 
of  oxygen.  You  will  observe  the  brilliant  effect  of  the 
combustion,  without  flame,  owing  to  the  bright  in- 
candescence of  the  particles  of  carbon  as  they  combine 
with  the  oxygen. 

The  dazzling  electric  light,  both  incandescent  and 
arc,  is  produced  by  similar  glowing  particles  of  car- 
bon. In  the  Edison  lamp,  a  slender  thread,  or  filament, 
of  carbon  is  raised  to  a  white  heat  by  the  electric  cur- 
rent; in  the  arc-lamp,  the  electricity  heats  the  particles 
at  the  ends  of  the  carbon-pencils,  and  the  white  hot 
sparks  of  carbon  flying  over  from  one  pole  to  the 
other  and  uniting  with  oxygen  as  they  go,  produce  the 
intense  light. 

Thus  the  blackest  thing  in  the  world  becomes  the 
source  of  our  whitest  light. 

After  learning  this, you  will  perhaps  not  be  so  greatly 


108  TIIK   WOULD    01      MATTKR. 

astonished  to  learn  that  although  this  amorphous  kind  of 
carbon,  known  as  charcoal  or  lamp  black,  is  so  dull  and 
black,  the  crystallized  form  of  carbon  is  the  most  splen- 
did mineral  in  the  world— tin-  Hashing  diamond. 

The  lustre  of  the  diamond  is  so  intense  that  a  special 
adjective  is  used  to  describe  it,  "adamantine"  The 
transparency  of  the  diamond  is  perfect,  unless,  as  often 
happen!,  there  it  some  impurity  in  the  stone.  A  very 
slight  admixture  of  a  foreign  substance  is  sufficient, 
however,  to  cloud  its  clearness,  dim  its  splendor,  and 
rhaiij-r  ils  color.  Owing  to  surh  impuritrvs  diamonds 
show  various  tints  of  color,  such  as  gray,  yellow,  green, 
and  brown ;  and  less  frequently  orange,  red,  blue,  or 
even  black. 

The  surest  test  of  a  diamond,  next  to  that  of  its 
chemical  properties,  it  its  hardness.  It  is  the  hardest 
known  substance;  and  can  be  scratched,  polished,  and 
cut  only  by  its  own  powder.  Its  specific  gravity  is 
about  ;.<>. 

Tin-  iiMi.il  I'm  in  of  Ilic  diamond 

crystal  is  a  solid,   bounded    by 

eight    equal    and     r<|nil.ilrial    tri- 
faces  (  Fig.  10,)  called  an 


The  art   of   cutting   diamonds 
was  not  known  in   Europe  until 
after   the  middle  of  the  fifteenth 
century,  when  it  was  invented  by  Louis  Van  Berguen, 
of  Bruges. 
India  has  long  been  celebrated  as  the  home  of  the 


A   PIECE   OF  CHARCOAL. 


109 


finest  diamonds,  and  in  India  the  most  famous  locality 
for  them  has  been  Golcondu;  though,  in  fact,  they  arc 
merely  cut  and  polished  there,  being  generally  found  in 
the  districts  lying  further  south  and  east.  Diamonds 
arc  also  found  in  Malacca,  Borneo,  and  other  parts  of 
the  East,  in  Bra/il,  Australia,  South  Africa,  Russia, 
and  the  United  States  of  America.  Small  and  inferior 


diamonds,  and  the  fragments  left  when  large  stones 
arc  cut,  are  called  "bort,"  and  command  a  ready  sale 
for  use  in  the  arts,  being  reduced  to  "dust"  in  a  steel 
mortar,  and  used  by  lapidaries  for  cutting  and  polishing 
all  sorts  of  gems.  Minute  fragments  of  bort  are  used 
for  making  the  fine  drills  by  which  small  holes  arc 
pierced  in  the  jewels  of  watches.  The  use  of  small 


i io  THE   WORLD   OF  MATTER. 

diamonds  for  cutting  glass  is  well  known.  For  this 
purpose  they  are  so  mounted  as  to  act  upon  the  glass, 
not  by  a  sharp  corner,  but  by  a  rounded  edge. 

Diamonds  are  cut  into  various  forms,  but  principally 
into  brilliants  and  rose  diamonds.  The  brilliant  cut 
is  the  most  expensive,  difficult,  and  beautiful.  It  has 
an  upper  face  or  "bezel,"  which  is  octagonal,  and  this  is 
surrounded  by  many  facets — and  as  a  rule  the  more  the 
better.  Some  varieties  of  the  brilliant  cut  are  shown 

in  Fig.  20. 

Rose  diamonds  have  a 
flat  base,  above  which  are 
two  rows  of  triangular 
facets,  the  six  uppermost 
uniting  in  a  point  to  form  a 
sparkling  pyramid.  Fig.  21. 

The  largest  diamond  known  weighs  367  carats — 
more  than  2^  ounces — and  belongs  to  the  rajah  of 
Mattan.  It  is  egg-shaped,  with  an  indented  hollow 
near  the  smaller  end. 

Many  years  ago  the  governor  of  Borneo  offered  for 
it  two  war-brigs  fully  equipped,  a  number  of  cannon, 
a  quantity  of  powder  and  shot,  and  $500,000  in  cash ; 
but  the  rajah  refused  to  part  with  it,  owing  to  a  super- 
stition which  connects  it  with  the  good  fortune  of  his 
family  and  the  health  of  his  province. 

The  Koh-i-noor,  once  a  boasted  possession  of  the 
great  Mogul,  now  belongs  to  the  English  crown.  It 
is  said  to  have  weighed  900  carats  in  the  rough,  but 
now  has  been  reduced  to  123. 


A   PIECE   OF  CHARCOAL.  lit 


The  Regent,  or  Pitt  diamond,  weighing  as  cut 
carats,  is  unrivaled  in  form  and  clearness.  It  was 
found  in  Golconda,  brought  from  India  by  the  grand- 
father of  Pitt,  the  first  Earl  of  Chatham,  and  by  him 
sold  to  the  duke  of  Orleans  for  .£13,000.  It  decorated 
the  hilt  of  the  first  Napoleon's  sword  of  state,  was 
captured  by  the  Prussians  at  the  battle  of  Waterloo, 
and  now  belongs  to  the  king  of  Prussia.  The  Vanci 
diamond,  weighing  106  carats,  belonged  to  Charles  the 
Bold,  duke  of  Burgundy,  who  wore  it  in  his  hat  at  the 
battle  of  Nancy,  where  he  fell. 

A  Swiss  soldier  found  it,  and  sold  it  to  a  clergyman 
for  a  gulden  —  about  half  a  dollar.  It  passed  into  the 
possession  of  Anton,  king  of  Portugal,  who  sold  it  for 
100,000  francs  ($20,000).  Later  it  became  the  prop- 
erty of  a  French  gentleman  named  Vanci. 

A  descendant  of  Vanci  being  sent  as  ambassador 
was  required  by  king  Henry  III.  to  leave  the  diamond 
as  a  pledge.  A  servant  was  accordingly  sent  to  carry 
it  to  the  king,  but  on  the  way  he  was  attacked  and 
murdered  by  robbers,  not,  however,  before  he  had  con- 
trived to  swallow  the  diamond  unobserved.  His 
master,  confident  of  his  fidelity,  caused  the  body  to  be 
opened,  and  recovered  the  jewel.  This  diamond  came 
into  the  possession  of  the  Crown  of  England,  and  James 
II.  carried  it  to  France  in  1688.  Louis  XV.  wore  it  at 
his  coronation.  In  1835  ^  was  purchased  by  a  Russian 
nobleman  for  nearly  half  a  million  dollars. 

The  following  interesting  account  of  the  South 
African  diamond  mines  is  condensed  from  the  report  of 
George  F.  Kunz,  for  1887. 


112  THE    WORLD   OF  MATTER. 

"The  author  of  the  Arabian  Nights  undoubtedly 
thought  he  was  imagining  the  most  improbable  thing 
when  he  described  the  'Valley  of  Diamonds,'  found  by 
Sindbad  the  Sailor.  Yet  when  compared  with  the  Afri- 
can mines  that  valley  pales  into  insignificance. 

"The  primitive  method  of  washing  was  carried  on  for 
centuries  by  thousands,  of  slaves  driven  by  the  merci- 
less whip  of  their  master;  but  improved  methods  have 
gradually  been  introduced.  Steam  railroads  were  run 
into  the  mine.  Millions  of  tons  of  reef  were  re- 
moved. Dynamite  was  substituted  for  powder. 

"After  the  broken  earth  is  raised,  it  is  put  on  the 
'sorting-ground,'  where  it  is  partly  disintegrated  by 
water  and  the  weather.  After  being  more  finely 
broken  up,  it  is  passed  down  into  large  vats  con- 
taining immense  wheels,  by  which  the  rock  is  finely 
divided.  So  accurately  and  powerfully  does  this  ma- 
chinery work,  that  all  the  diamonds,  even  those  of 
the  size  of  a  pin-head,  are  saved.  Thirteen  million 
gallons  of  water  are  annually  hoisted  from  the  Kim- 
berly  mine.  Ten  thousand  natives,  2,500  horses,  mules, 
and  oxen,  and  350  steam-engines  are  employed. 

"During  the  last  ten  years,  the  South  African  mines 
have  yielded  27,878,587  carats,  valued  at  .£31,717,341. 

"Before  the  organization  of  the  great  companies 
which  now  work  these  mines  as  systematically  and 
economically  as  a  woolen-mill,  it  is  believed  that  about 
one-quarter  of  the  diamonds  found  were  stolen  by  the 
workmen.  The  natives  use  the  most  ingenious  methods 
for  concealing  the  precious  gems.  On  one  occasion 


A    PIECE    OF    CHARCOAL.  113 

some  officers,  suspecting  that  a  Kafir  had  stolen  dia- 
monds, gave  chase  and  caught  him,  just  after  he  had 
shot  one  of  his  oxen.  No  diamonds  were  found  upon 
him,  but  he  got  off  with  them  nevertheless,  for  he  had 
cunningly  loaded  his  gun  with  them,  and  after  the 
departure  of  the  officers  he  had  the  satisfaction  of 
digging  them  out  ot  the  body  of  his  dead  ox, 

"More  diamonds  weighing  over  75  carats  after  cut- 
ting have  been  found  since  the  African  mines  were 
opened  than  were  ever  known  before.  On  March  28, 
1888,  there  was  found  in  the  De  Beers  mine  an  oc- 
tahedral crystal  of  diamond  weighing  428^  carats. 

"It  was  valued  at  $15,000.  From  its  form  it  is  be- 
lieved that  it  can  be  cut  into  a  brilliant  of  200  carats; 
hence  it  will  be  the  largest  known." 

Besides  the  forms  already  described,  namely,  char- 
coal, coke,  lamp-black,  bone-black,  coal,  lignite  and 
diamond,  carbon  also  occurs  in  the  form  known  as 
graphite,  plumbago,  or  "black-lead,"  which  is  used  by 
every  one  in  ordinary  pencils. 

Of  course  there  is  no  lead  about  it;  it  is  only  a  form 
of  carbon.  It  can  be  artificially  prepared  by  dissolv- 
ing charcoal  in  melted  iron,  from  which  on  cooling  the 
carbon  is  deposited  as  graphite.  Graphite  has  a  gray- 
ish black  streak,  and  a  metallic  lustre,  although  it  is  not 
a  metal.  This  would  be  indicated  by  its  brittleness,  as 
well  as  by  its  infusibility. 

It  has  a  greasy  or  unctuous  "feel,"  and  is  largely  used 
as  a  lubricant.  It  is  not  found  pure,  but  contains  a 
small  admixture  of  iron,  silica,  lime,  alumina,  etc.  It 
8 


ti4  TH£    WORLD   OF  MATTER. 

sometimes  occurs  in  tabular  or  scaly  hexagonal  crystals, 
but  usually  massive.  It  is  much  less  combustible  than 
hard  coal,  and  burns  with  difficulty,  even  before  the 
blow-pipe,  so  that  it  is  very  useful  for  the  manufacture  of 
melting-pots  or  "crucibles,"  which  have  to  withstand 
great  heat.  For  this  purpose,  however,  it  is  mixed 
with  half  its  weight  of  clay.  Graphite  is  the  chief 'in- 
gredient in  stove-polish. 

QUESTIONS    ON    CHAPTER    IO. 

1.  In  what  substances  is  carbon  found? 

2.  What  are  the  three  leading  forms  of  carbon? 

3.  Describe  charcoal  and  its  uses. 

4.  Mention  other  similar  forms  of  carbon. 

5.  Explain  the  brilliancy  of  ordinary  flame. 

6.  Of  what  is  sugar  composed? 

7.  Explain  the  brightness  of  the  electric  light. 

8.  Describe  the  diamond. 

9.  What  is  the  usual  form  of  its  crystal? 

10.  What  is  "bort  ?" 

11.  Describe  graphite.     Its  uses? 

12.  Form  of  its  crystals. 


CARBON,  CONTINUED. 


CHAPTER  XI. 

CARBON,    CONTINUED. 

In  the  preceding  chapter  we  studied  carbon,  one  of 
the  most  abundant,  common,  and  wonderful  elements. 
We  found  it  appearing,  as  if  by  magic,  under  various 
forms  of  the-  utmost  dissimilarity:  as  soft  as  velvet 
and  as  black  as  night  in  lamp-black;  harder  than  steel, 
and  as  bright  as  day  in  the  diamond ;  now  the  chief  con- 
stituent in  our  illuminating  oils  and  in  our  fuels,  on  ac- 
count of  its  brilliant  and  fiery  combustion  with  oxygen; 
and  again  used  for  crucibles,  because  in  the  form  of 
graphite  it  will  neither  burn  nor  melt;  in  the  form  of 
"bort"  we  saw  it  used  to  cut  and  scratch,  and  rasp  the 
hardest  substances,  and  again  as  graphite  we  found  it 
used  instead  of  oil  to  prevent  the  friction  of  wheels  and 
shafts.  It  is  the  hardest  and  the  softest,  the  dullest  and 
the  brightest,  the  cheapest  and  the  dearest,  the  roughest 
and  the  smoothest;  in  a  word,  the  most  contradictory 
element  in  nature. 

How  then  do  we  know  its  identity?  Why  are  we 
certain  that  charcoal  and  graphite  and  the  diamond  are 
not  really  three  distinct  minerals  instead  of  three  forms 
of  the  same  mineral? 

In  the  first  place,  notwithstanding  these  marked  dif- 
ferences there  are  also  certain  marked  resemblances' be- 


Ii6  THE   WORLD   OF  MATTER. 

tween  these  forms  of  carbon.  They  are  insoluble  in 
all  known  liquids;  they  are  tasteless,  inodorous,  and 
infusible;  and  wnen  heated  without  free  access  of  air, 
they  remain  unchanged  unless  the  temperature  is  very 
high. 

In  the  second  place,  we  know  that  they  are  varie- 
ties of  the  same  substance,  because  if  we  burn  the  same 
weight  of  diamond,  graphite,  and  charcoal,  we  obtain 
in  each  case  the  same  substance, "carbon  dioxide,"  CO2. 


Fig.    22. 


In  each  case  the  oxygen  of  the  product  comes  from 
the  air,  and  in  each  case  the  weight  of  the  carbon 
in  the  product  is  exactly  equal  to  the  weight  of  the 
diamond  or  graphite  or  charcoal  consumed. 

I  will  not  ask  you  to  verify  this  statement  by  burning 
a  diamond,  unless  you  have  plenty  of  them  to  spare; 
but  that  experiment  has  repeatedly  been  performed,  and 
always  with  the  same  result.  You  may,  however,  with 
much  profit  make  the  experiment  of  combining  char- 


CARBON,  CONTINUED.  117 

coal  with  oxygen,  in  the  following  manner:  Put  a 
small  piece  of  charcoal  into  a  hard  glass  tube.  Heat 
this  tube  by  an  alcohol  flame,  or  a  gas-jet,  at  the  same 
time  passing  oxygen  through  it.  Pass  the  resulting 
gas  into  clear  lime-water.  Arrange  the  apparatus  as 
shown  in  Fig.  22. 

A  is  a  bottle  containing  oxygen ;  B  is  a  hard  glass 
tube  containing  the  charcoal;  C  is  the  jar  of  clear  lime- 
water.  The  reaction  which  takes  place  is  represented 
thus: 

Ca08H8  -f  CO,  =  CaCOs  +  H8O 
Lime-  Carbon  Calcium  Water, 
water.  dioxide.  carbonate. 

That  is,  the  oxygen  passing  over  the  heated  charcoal 
combines  with  it  to  form  a  new  gas,  and  this  shows 
itself  on  passing  into  the  lime-water  by  combining  with 
the  lime  in  solution,  forming  carbonate  of  lime,  which 
is  insoluble  in  the  water,  and  therefore  sinks  as  a  white 
chalky  powder.  Now,  no  other  gas  except  carbon  di- 
oxide acts  in  this  way  with  lime-water. 

Hence  we  may  conclude  that  the  gas  formed  is  car- 
bon dioxide.  This  is  a  useful  test,  and  whenever  under 
ordinary  circumstances  an  unknown  gas  passing  into 
lime-water  produces  an  insoluble  substance,  we  may 
conclude  that  the  gas  is  carbon  dioxide. 

Notice  in  passing  the  significance  of  the  chemical  ter- 
mination— ate.  I  have  already  shown  you  that  the  ter- 
mination— ide^  is  used  in  names  of  the  compounds  of 
two  substances.  Thus  every  oxide  is  a  compound  of 
oxygen  with  one  other  element  j  every  sulphide  is  a 


Ii8  THE    WORLD    OF   MATTER. 

compound  of  sulphur  with  one  other  element,  etc.  Now 
the  termination — ate,  is  used  in  names  of  the  compounds 
of  three  substances,  one  of  which  is  always  oxygen, 
and  another  of  which  is  always  indicated  by  that  part 
of  the  name  which  precedes  the  termination — ate. 
Thus  every  carbonate  is  a  compound  of  oxygen,  car- 
bon, and  one  other  substance.  Every  sulphate  is  a  com- 
pound of  oxygen,  sulphur,  and  one  other  substance,  etc. 
The  name  of  the  third  element  in  every  such  compound  is 
written  after,  and  connected  by  the  word  "of ;''  thus, 
carbonate  of  calcium;  sulphate  of  lead,  etc.;  or  it  may 
equally  well  be  written  before,  as  calcium  carbonate, 
lead  sulphate,  etc.  What  is  the  composition  of  "silver 
nitrate  ?" 

Now,  by  the  lime-water  test,  as  I  was  saying,  it  has 
been  proved  that  charcoal,  graphite,  and  the  diamond 
are  all  varieties  of  the  same  substance,  carbon,  because, 
all  of  them  when  combined  with  oxygen  form  a  gas 
which  when  passed  into  lime-water  combines  with  the 
lime  and  forms  the  insoluble  substance,  carbonate  of 
lime.  This  property  of  carbon,  and  other  elements,  by 
virtue  of  which  they  exist  in  dissimilar  forms,  is  called 
allotropism. 

Before  leaving  our  study  of  carbon  we  must  notice 
that  its  affinity  for  oxygen  is  so  great  that,  under  proper 
conditions,  it  is  able  to  abstract  the  oxygen  from 
oxides. 

This  you  may  prove  by  the  following  experiment: 

Mix  two  or  three  grains  of  powdered  copper  oxide, 
CuO,  with  about  one-tenth  its  weight  of  powdered 


CARBON,  CONTINUED. 


119 


-  23- 


charcoal.     Heat  the   mixture   in  a  tube   fitted   with  a 
small  outlet  tube  as  shown  in  Fig.  23. 

Pass  the  gas  which  is  given 
.off  into  clear  lime-water,  con- 
tained in  a  test-tube.  Is  it  car- 
bon dioxide?  What  evidence 
have  you  that  oxygen  has  been 
removed  from  the  copper 
oxide? 

Does  the  substance  left  in 
the  tube  suggest  the  metal 
copper  ? 

The  reaction  between  the 
charcoal  and  the  copper  oxide 
2CuO+C=2Cu+CO2. 
This  abstraction  of  oxygen  from  a  compound  is 
called  reduction.  Hence  carbon,  which  effects  it,  is 
called  a  reducing  agent.  It  is  extensively  used  in  ex- 
tracting metals  from  their  ores,  which  are  usually  oxides. 
Thus  iron  occurs  in  nature,  not  pure,  but  usually  in 
combination  with  oxygen.  In  order  to  get  the  pure 
metal  the  oxygen  must  be  extracted.  This  is  accom- 
plished by  heating  the  ore  with  some  form  of  carbon, 
either  charcoal  or  coke. 

To  conclude  this  lesson,  let  us  study  that  most  im- 
portant compound  of  carbon  and  oxygen,  which  we 
have  already  discovered  and  learned  to  recognize  as 
carbon  dioxide,  CO2.  It  is  commonly  called  carbonic 
acid.  It  has  already  been  shown  that  carbon  dioxide  is 
formed  by  the  combustion  of  charcoal,  In  a  similar 


is  represented  thus 


120 


THE   WORLD   OF   MATTER. 


manner  it  can  be  shown  that  this  gas  is  formed  when- 
ever any  ordinary  material  is  burned.  For  example, 
hold  an  empty  bottle  over  the  chimney  of  a  burning 
lamp  so  that  it  may  receive  the  products  of  the  com- 
bustion of  the  oil. 

You  will  soon  find  something  besides  ordinary  air  in 
the  bottle.  Pour  a  little  clear  lime  water  into  it,  nnd 
shake  it  up.  Do  you  see  any  evidence  of  the  presence 
of  carbon  dioxide? 

Burn  a  piece  of  paper  in  a  jar,  pour  in  a  little  lime- 
water,  and  observe  the  result. 

Consider  now  what  is  constantly  going  on  in  your 
own  body  when  you  breathe.  Perhaps  you  have  never 
thought  of  it  at  all ;  perhaps  you  have  supposed  that  in 
breathing  you  simply  draw  a  quantity  of  air  into  the 
lungs  and  breathe  the  same  quantity  of  air  out  again.  Ti  y 
this  experiment:  Arrange  a  bottle 
or  flask  of  lime-water  as  in  Fig.  24. 
Placing  your  lips  on  the  tube  #, 
you  can  either  draw  the  outside  air 
through  the  lime-water,  or  blow  the 
air  from  your  lungs  through  it.  Try 
first  the  experiment  of  drawing  the 
outside  air  through  the  water.  Ob- 
serve that  so  long  as  you  do  this  no 
effect  is  produced  upon  the  water. 
Now  throw  the  air  from  your  lungs 
through  the  lime-water  several  times 
See  how  the  lime-water  grows  chalky, 
This  teaches  you  a  very  important  lesson. 


Fig.  24. 


in  succession. 


CARBON,  CONTINUED.  121 

The  air  that  you  breathe  out  is  no  longer  pure,  but 
contains  carbon  dioxide.  A  sort  of  combustion  is  going 
on  in  your  lungs;  the  oxygen  of  the  air  is  combining 
with  a  portion  of  the  carbon  contained  in  your  blood, 
forming  carbon  dioxide,  which  is  expelled  from  your 
body  when  you  breathe.  This  combustion  of  oxygen 
and  carbon  in  the  lungs  is  one  of  the  means  by  which 
the  body  is  so  \\Tonderfully  heated,  that  in  summer  and 
winter  it  is  maintained  at  the  most  uniform  tempera- 
ture, and  with  the  least  expenditure  of  fuel.  In 
twenty- four  hours  the  lungs  of  a  man  convert  seven 
ounces  of  carbon  into  carbon  dioxide. 

Just  here,  I  must  call  your  attention  to  another  prop- 
erty of  this  gas.  Into  a  jar  of  carbon  dioxide  plunge 
a  lighted  taper.  It  is  at  once  extinguished.  If  a  mouse 
or  bird  be  dropped  in  the  gas,  its  life  goes  out  like  the 
flame  of  the  taper.  One  or  two  breaths  from  your 
lungs  will  furnish  enough  gas  for  this  experiment. 

Set  a  bottomless  jar  or  bottle  in  a  vessel  of  water.  Close 
it  with  a  tight  cork,  in  which  a  small  tube  is  closely  fitted. 

Now  inhale  the  air  from  the  jar,  and  breathe  it  back, 
as  shown  in  the  figure.  Even  one  inspiration  is  enough 
to  spoil  the  air  so  that  a  taper  will  not  burn  in  it.  This 
forcibly  illustrates  the  necessity  of  an  abundant  supply 
of  fresh  air  in  our  homes  and  schools  and  churches.  It 
proves  the  need  and  indicates  the  character  of  good 
ventilation. 

The  carbon  dioxide  must  be  removed  as  fast  as  it  is 
breathed  out,  and  plenty  of  air  containing  its  full  meas- 
ure of  oxygen  must  be  supplied. 


122  THE   WORLD   OF  MATTER. 

It  must  not  be  supposed,  however,  that  carbon  di- 
oxide is  a  poisonous  gas  any  more  than  nitrogen  is. 

Animals  die  in  it  merely  because  of  a  lack  of  oxy- 
gen; they  suffocate,  as  they  do  in  water  or  as  they 
would  in  nitrogen.  Most  of  the  bad  effects  of  breath- 
ing the  air  of  ill-ventilated  rooms,  such  as  headache, 
drowsiness,  etc.,  are  caused  by  other  impurities  con- 
tained in  the  breath. 

The  total  amount  of  carbon  dioxide  formed  by  breath- 
ing is  almost  alarming.  Faraday  estimates  that  the 
lungs  of  London  alone  pour  out  54.8  tons  of  this  gas 
every  twenty-four  hours! 

Add  to  this  the  vast  quantities  that  result  from  all 
the  combustion  that  is  constantly  going  on,  and  you 
will  wonder  that  in  the  course  of  ages  the  whole  at- 
mosphere does  not  become  unfit  to  breathe.  What 
prevents  it? 

Just  here  comes  in  one  of  the  most  beautiful  and 
wonderful  contrivances  of  nature.  This  gas  so  deadly 
to  animal  life  is  the  very  life  and  support  of  plants. 
All  the  plants  that  grow  upon  the  earth  absorb  car- 
bon from  the  air.  By  the  aid  of  sunlight  and  sun  heat, 
they  decompose  the  carbon  dioxide  which  animals 
breathe  out,  and  build  up  from  it  the  complex  com- 
pounds of  carbon  which  form  their  tissues,  and  set  free 
again  the  oxygen  that  is  so  necessary  for  animal  life. 
Give  to  plants  a  pure  air  like  that  which  is  best  for  us, 
and  they  cannot  live  in  it;  give  them  carbon  dioxide 
and  x>ther  matters  and  they  live  and  rejoice. 

From  this  our  dependence  upon  the  sun  is  made  evi- 


CARBON,  CONTINUED.  123 

dent.  Every  living  thing  is  dependent  upon  the  decom- 
position of  carbon  dioxide  by  plants.  This  decompo- 
sition cannot  be  effected  without  the  aid  of  the  sun.  If 
the  sun  should  stop  shining,  all  earthly  life  would 
cease. 

We  have  seen  that  when  carbon  dioxide  passes  into 
lime-water  it  combines  with  the  lime  to  form  carbonate 
of  calcium,  or  chalk.  As  it  is  a  poor  rule  that  will  not 
work  both  ways,  we  ought,  therefore,  to  be  able  to  de- 
compose chalk,  or  any  form  of  carbonate  of  lime,  and 
get  the  carbon  dioxide  again.  And  this  we  can  easily 
do.  If  some  moistened  chalk  be  put  into  a  retort  and 
heated  red-hot  carbon  dioxide  is  driven  off. 

A  simpler  method  of  decomposing  carbonates,  how- 
ever, is  by  the  use  of  an  acid. 

Into  a  jar  containing  a  few  small  chippings  of  chalk, 
limestone,  marble,  or  oyster-shell—all  varieties  of  car- 
bonate of  calcium — pour  a  little  hydrochloric  acid.  A 
brisk  boiling — in  this  case  called  effervescence — imme- 
diately begins. 

It  is  not  steam,  however,  that  is  bubbling  up,  but  a 
gas.  Test  the  contents  of  the  jar  with  a  taper.  The 
flame  is  instantly  extinguished.  Pass  some  of  the  gas 
into  lime-water;  the  chalky  carbonate  is  formed. 

Here  then  we  have  again  carbon-dioxide,  the  very 
same  gas  we  formerly  produced  by  the  direct  combina- 
tion of  carbon  and  oxygen ;  and  by  this  action  of  the 
acid  upon  a  carbonate  we  obtain  tire  gas  more  readily, 
and  in  great  abundance. 

Having    it,  now,   in   sufficient    quantity,   familiarize 


124  THE   WORLD   OF   MATTER. 

yourself  with  it  by  as  many  experiments  and  tests  as 
you  can  invent. 

Ascertain  whether  it  is  heavier  or  lighter  than  air. 
See  whether  you  can  pour  it  out  of  a  jar  as  you  can 
water.  Pour  some  on  a  candle-flame.  Balance  a  jar 
on  a  pair  of  scales  and  pour  some  of  the  gas  into  it. 
Does  it  affect  the  scales? 

Carbon  dioxide  dissolves  in  water,  one  volume  of  gas 
dissolving  in  about  its  own  volume  of  water  at  the 
ordinary  temperature.  When  the  pressure  is  increased 
more  gas  dissolves;  and  when  the  pressure  is  removed 
the  gas  again  escapes.  The  "soda-water"  of  the  drug- 
gists is  simply  water  charged  with  carbon  dioxide  under 
pressure. 

Much  of  the  life  and  sparkle  of  ordinary  spring 
water  is  due  to  carbon  dioxide  dissolved  in  it.  Spring 
water  is  therefore  a  sort  of  natural  soda-water.  Rain- 
water, like  boiled  or  distilled  water,  has  a  flat,  insipid 
taste,  but  as  it  trickles  down  the  mountain-side,  and 
dashes  from  ledge  to  ledge  of  rock,  it  dissolves  the 
gases  in  the  air  and  becomes  thus  naturally  aerated. 

QUESTIONS  ON  CHAPTER   II. 

1.  How  can  the  identity    of  charcoal,  graphite,  and 
diamond  be  proved? 

2.  What  is  the  product  of  the  combustion  of  car- 
bon with  oxygen? 

3.  What  effect  has  this  gas  on  lime-water? 

4.  What  is  the  significance  of  the  termination  "ate?" 

5.  What  is  allotropism  ? 


CARBON,  CONTINUED.  125 

6.  What  can  you   say   of   carbon   as   a   "reducing- 
agent?" 

7.  How  is  air  changed  by  breathing? 

8.  Describe  carbon  dioxide. 

9.  What  is  the  cause  of  the  necessity  for  ventilation  ? 

10.  Why  does    not  the    whole    atmosphere   become 
tainted  with  carbonic  acid  ? 

11.  How  can  carbon  dioxide  be  obtained  from  lime- 
stone or  chalk? 

12.  What  is  "soda-water?" 


126  THE  WORLD  OF  MATTER. 


CHAPTER  XII. 

A    PIECE    OF    MARBLE. 

You  will  remember  that  we  were  led  to  our  study 
of  carbon  by  rinding  bits  of  charcoal  in  a  handful  of 
earth  which  we  heated.  In  this  earth  we  -have  also 
found  water  and  quartz. 

Let  us  now  examine  it  further:  Dry  a  tablespoon- 
ful  of  garden-soil  without  burning  it,  and  pour  a  few 
drops  of  hydrochloric  acid  upon  it.  If  your  garden  is 
like  mine  you  will  notice  a  brisk  effervescence;  which 
will  remind  you  of  the  experiment  described  in  the 
preceding  chapter,  by  which  we  obtained  carbon  dioxide 
by  treating  carbonate  of  lime  with  hydrochloric  acid. 

We  then  used  lime  dissolved  in  water  as  a  test  for 
the  carbon  dioxide,  and  decided  that  any  gas  which 
passing  into  lime-water  at  ordinary  temperature  ren- 
ders it  chalky  is  carbon-dioxide;  and  we  learned  that 
the  chalk  thus  formed  is  carbonate  of  calcium. 

With  this  knowledge  we  may  now  work  backward, 
and  make  the  production  of  carbonic  oxide  by  the  action 
of  hydrochloric  acid  upon  a  mineral  a  test  for  carbon- 
ate of  calcium;  for  this  is  the  only  common  mineral 
which  effervesces  freely  with  dilute  hydrochloric  acid 
at  ordinary  temperatures. 

We,  therefore,  may   reasonably    conclude   that   our 


A   PIECE   OF   MARBLE.  127 

soil  contains  calcium  carbonate,  and  proceed  to  study 
this  substance  in  some  detail.  It  will  be  convenient,  as 
in  the  case  of  quartz,  to  use  larger  specimens  than  the 
minute  grains  mingled  with  the  soil,  and  we  will  there- 
fore take  a  piece  of  white  marble — specimen  No.  20  in 
the  collection. 

Repeating  the  experiment  with  hydrochloric  acid  we 
obtain  again  a  plentiful  supply  of  carbon  dioxide,  which 
we  allow  to  escape,  however,  as  we  are  now  more 
interested  in  the  other  elements  in  the  carbonate.  The 
reaction  is  expressed  as  follows: 

CaCo3+2HCl==C08-fH2O+CaCls. 

This  means  that  calcium  carbonate  and  hydrochloric 
acid  give,  besides  the  carbon  dioxide,  water  and  calcium 
chloride.  The  chloride  is  dissolved  in  the  water. 

Evaporate  the  solution  to  dryness. 

The  colorless  needle-shaped  crystals  remaining  are 
calcium  chloride,  still  combined  with  a  portion  of 
water.  In  this  condition  it  is  called  hydrated  calcium 
chloride.  Expose  this  substance  to  the  air.  Observe 
how  rapidly  it  becomes  moist  by  absorbing  water  from 
the  air.  This  property  makes  it  valuable  for  drying 
gases.  In  many  experiments,  gases  containing  undesira- 
ble moisture  are  passed  through  tubes  containing  cal- 
cium chloride,  which  absorbs  the  water  and  leaves  the 
gases  dry.  If  hydrated  calcium  chloride  be  strongly 
heated  it  fuses  and  parts  with  all  its  water,  becoming 
simply  CaCl2. 

Calcium  chloride  consists  of  two  very  important  ele- 


128  THE   WORLD   OF', MATTER; 

inents>  calcium^  which  we  are  now  specially  in  search 
of,  and  chlorine,  a  gas  which  we  shall  consider  later. 

Unfortunately  it  is  not  easy  to  separate  them.  I  say 
"unfortunately,"  for  it  is  important  for  you  to  become 
familiar  with  the  leading  elements  in  their  purity,  as 
far  as  possible.  The  analysis  of  calcium  chloiide, 
though  difficult,  is  not  impossible,  and  is  effected  by 
fusing  it,  and  passing  a  powerful  current  from  an  elec- 
tric battery  through  it.  If  you  have  some  friend  who 
is  an  expert  chemist  or  mineralogist,  it  will  be  worth 
your  while  to  get  him  to  perform  the  experiment  for 
you.  You  will  then  see  the  calcium  separating  from 
the  chlorine  in  the  form  of  minute  drops  or  globules.  It 
is  a  yellowish-white  metal,  between  gold  and  lead  in 
hardness.  It  graduaUy  grows  dull,  or  tarnishes,  on  .ex- 
posure to  the  air. 

In  order  to  keep  it  bright  it  is  kept  under  naptha.  It 
can  be  rolled  into  sheets  and  hammered  into  leaves.  At 
a  red  heat  it  melts  and  burns  with  a  dazzling  light,  ac- 
companied with  showers  of  sparks.  When  brought 
into  contact  with  wa^er  it  unites  strongly  with  the  oxy- 
gen, forming  lime,  CaO,  and  setting  the  hydrogen  free. 
This  is  another  pi  oof  of  the  composition  of  water,  and 
is  a  very  interesting  and  instructive  experiment.  You 
remember  that  we  have  already  seen  that  the  oxygen  of 
water  will  desert  its  comrade,  hydrogen,  for  the  sake  of 
uniting  with  red-hot  iron.  The  attraction  between 
oxygen  and  calcium  is  so  much  greater  that  oxygen 
combines  with  it  at  ordinary  temperature. 

Returning   now   to  our  marble,  CaCO3,  we  will  try 


A   PIECE   OF   MARBLE.  129 

to  decompose  it  without  the  help  of  acid.  Put  a  piece 
of  marble  into  a  stove  or  furnace,  and  leave  it  over 
night.  On  taking  it  out  you  at  once  perceive  a  decided 
change  in  its  appearance,  and  a  more  decided  change 
in  its  properties.  It  has,  in  fact,  been  converted  into 
quicklime,  the  carbon  dioxide  having  been  driven  off 
by  heat. 

The  decomposition  is  represented  thus: 

CaC03  CaO  +  CO2 

Calcium  Carbonate.       Quicklime.         Carbon  dioxide. 

Expose,  now,  one-half  of  the  quicklime  to  the  air, 
and  place  the  remainder  in  a  cup  half  full  of  water. 

The  portion  exposed  to  the  air  gradually  absorbs 
both  moisture,  H^O,  and  carbon  dioxide,  CO2,  and  is 
resolved  again  into  calcium  carbonate,  in  the  form  of 
a  white  powder.  This  is  commonly  called  air-slaked 
lime. 

The  portion  put  into  the  cup  rapidly  combines  with 
the  water,  becomes  very  hot,  crumble^ into  a  fine  pow- 
der, and  is  converted  into  the  hydroxide  or  hydrate  of 
calcium.  The  result  of  this  water -slaking  is  thus  repre- 
sented : 

CaO-fH2O=CaO2Hs 

This  substance  is  partially  soluble  in  water,  and  forms 
lime-water.  Pour  the  slaked  lime  from  your  cup  into 
a  jar,  or  wide-mouthed  bottle,  containing  perhaps  a  pint 
of  water.  The  unclissolved  lime  will  settle  to  the  bot- 
tom. After  some  hours  the  solution  above  will  become 
clear.  Pour  this  off  carefully  for  experiment. 
9 


i$6  THE   WORLD   OF  MATTER. 

What  takes  place  when  some  of  the  solution  is  ex- 
posed to  the  air?  When  the  gases  from  the  lungs  are 
passed  through  it?  When  carbon  dioxide  is  passed 
through  it?  When  dilute  sulphuric  acid  is  added? 

Slaked  lime  mixed  with  sand  is  used  for  mortar, 
whitewash,  and  plastering.  When  the  mortar  is  spread 
and  exposed  to  the  air  it  takes  up  carbon  dioxide,  and 
thus  the  calcium  oxide,  or  lime,  becomes  calcium  car. 
bonate  again,  and  hardens  into  stone. 

Notice  right  here  a  curious  property  of  carbon 
dioxide.  We  have  repeatedly  seen  that  a  small  quan- 
tity of  it,  passed  into  lime-water,  unites  with  the  lime, 
forming  the  chalky  carbonate  of  calcium.  Now  repeat 
that  experiment,  but  allow  the  gas  to  pass  into  the  lime- 
water  for  a  longer  time.  You  will  be  surprised  to  ob- 
serve that  the  chalky  water  gradually  grows  clear  again. 
The  explanation  of  this  phenomenon  is  found  in  the 
fact  that  water  saturated  with  carbon  dioxide  dissolves 
the  carbonate.  To  this  property  we  owe  the  formation 
of  caves  in  limestone  regions  with  their  beautiful 
stalactites  which  depend  like  icicles  from  the  roof,  and 
the  curious  stalagmites  which  stand  up  like  inverted 
icicles  from  the  floor.  Water  containing  carbon  dioxide 
trickles  through  crevices  and  dissolves  away  the 
limestone  little  by  little  until  in  the  course  of  ages 
large  c'aves  are  formed.  Then  the  water  holding  cal- 
cium carbonate  in  solution  drips  slowly  from  the  roof, 
and  as  the  water  evaporates  little  particles  of  the  carbonate 
are  deposited,  until  the  long  glistening  stalactites  are 
formed;  while  the  drops  that  fall  to  the  floor  build  up 


A   PIECE   OF  MARBLE.  131 

in  like  manner  the  crystalline  stalagmites  in  many 
fantastic  shapes. 

The  following  simple  experiment  reveals  a  property 
of  lime  or  calcium  oxide  which  you  might  not  other- 
wise observe;  namely,  its  power  in  counteracting  the 
effect  of  an  acid. 

The  most  common  test  for  acids  depends  upon  the 
fact  that  they  instantly  change  the  color  of  certain  sub- 
stances. One  of  the  substances  whose  color  is  most 
easily  and  noticeably  changed  by  an  acid  is  called 
litmus.  Litmus  is  a  coloring  matter  which  is  obtained 
from  several  sorts  of  lichen  or  fungus.  The  lichens  are 
powdered  and  steeped  in  ammonia-water  until  they  are 
decomposed. 

After  further  treatment,  not  necessarily  described 
here,  a  peculiar  purple  dye  is  obtained,  which  is  the 
litmus  of  commerce. 

The  interesting  fact  about  this  litmus  is  that  upon  the 
addition  of  any  acid  it  turns  red;  and  again,  upon  the 
addition  of  lime  or  any  alkali,  it  turns  blue.  This  you 
should  now  prove  by  several  experiments.  You  will 
find  in  the  collection  accompanying  this  book  (specimen 
No.  21)  apiece  of  blue  "litmus-paper,'*  which  is  simply 
a  piece  of  ordinary  unsized  paper,  dyed  with  an  alcoholic 
solution  of  litmus  and  treated  with  some  alkali. 

You  can  turn  a  piece  of  this  blue  paper  red  by 
moistening  it  with  an  acid,  or  more  easily  by  moistening 
it  and  holding  it  over  burning  sulphur;  a  burning  match 
will  answer  the  purpose.  You  can  get  this  paper,  both 
red  and  blue,  at  a  drug-store,  or,  better,  you  can  buy 
litmus  and  prepare  it  yourself. 


i$2  THE  WORLD  OF  MATTER. 

Now,  to  see  the  effect  of  lime,  moisten  a  piece  of  red 
litmus-paper,  and  place  a  few  grains  of  quicklime 
upon  it;  it  turns  blue.  Try  the  effect  cf  a  little  pow- 
dered marble. 

Now  heat  some  of  the  marble  red-hot,  either  by  lay- 
ing it  on  a  piece  of  charcoal  and  applying  a  blcw-pipe 
flame,  or  by  holding  it  in  the  flame  with  a  pair  of  for- 
ceps. 

Place  this  burned  marble  upon  the  moistened  red 
paper,  and  note  the  effect.  Here  is  another  proof  that 
calcium  carbonate,  when  heated,  parts  with  if.s  carbon 
dioxide,  and  become  calcium  oxide,  or  quicklime. 

Instead  of  using  the  paper,  you  may  try  the  same 
experiments  with  more  striking  results  upon  a  glass 
full  of  the  red  solution  of  litmus. 

It  is  to  this  antacid  action  of  the  lime  fchit  it 
owes  its  valuable  medicinal  properties,  lime-water  be- 
ing one  of  the  best  remedies  for  acidity  and  irritability 
of  the  stomach. 

In  the  ashes  which  remain  after  the  combustion  of 
any  vegetable  matter  a  proportion  of  lime  is  found. 
This  shows  that  calcium  oxide  is  one  of  the  most  im- 
portant plant-foods,  and  indicates  the  use  of  lime  as  ^ 
fertilizer. 

The  carbonate  is  sometimes  applied  without  previous 
preparation,  in  the  form  of  marl  or  chalk;  but  usually 
after  having  been  calcined,  and  reduced  to  the  powdered 
oxide  by  slaking. 

The  quantity  of  calcined  lime  used  varies  from  three 
';o  eight  tons  to  the  acre ;  the  larger  quantity  being  re- 


A   PIECE   OF   MARBLE.  133 

quired  for  "strong"  land,  or  land  holding  much  vegeta- 
ble matter.  The  fertilizing  effect  of  lime  is  due  even 
more  to  its  chemical  effects  upon  the  soil  than  to  the 
food  it  directly  affords  to  the  crops.  It  promotes  the 
decomposition  of  all  kinds  of  vegetable  matter  in  the 
soil,  and  corrects  any  acidity  present,  and  thus  tends  to 
destroy  those  weeds  which  flourish  in  an  acid  soil.  On 
certain  kinds  of  soil,  the  finer  grasses  do  not  thrive  un- 
til the  land  has  been  limed.  Lime  is  the  only  reliable 
cure  for  "finger-and-toe,"  "club-root,"  "ambury,"  in 
turnips. 

In  the  preceding  chapter  we  learned  that  the  bril- 
liancy of  the  electric  light  is  due  to  the  incandescence 
of  some  highly  heated  infusible  substance,  usually  carbon. 

Lime  is  infusible,  and  when  strongly  heated  yields  a 
light  fairly  rivalling  the  electric  lamp.  A  jet  of  oxygen 
and  hydrogen  burning  together  in  an  intensely  hot 
Hume  is  directed  against  a  cylinder  of  lime.  The  light 
produced  in  this  way  has  been  seen  for  more  than  one 
hundred  miles.  It  is  called  the  "Drummond  light," 
from  its  inventor,  Captain  Thomas  Drummond. 

To  calcium  carbonate,  the  mineralogists  have  given 
the  name  calcitc.  In  nature  calcite  occurs  as  marble, 
chalk,  limestone,  shells,  corals  and  pearls,  and  in  a 
crystallized  form  known  as  calc-spar. 

In  all  its  forms  it  is  readily  distinguished  from  quartz 
by  its  inferior  hardness,  and  by  its  effervescence  with 
acids.  Its  hardness  is  2.7.  Shells,  corals,  and  pearls, 
being  evidently  animal  products,  will  more  properly  be 
considered  in  the  succeeding  volume  of  this  series. 


134  THE   WORLD   OF  MATTER. 

Common  limestone,  chalk,  and  marble  are  also 
largely  derived  from  organic  structures,  but  for  the 
present  they  may  be  considered  as  ordinary  minerals. 

Limestones  are  either  compact  or  granular,  the  com- 
pact form  breaking  with  a  smooth  surface,  often  shell- 
like  or  conchoidal.  Granular  limestones,  of  which, 
indeed,  marble  is  a  fine  variety,  are  crystalline,  and 
break  with  a  more  or  less  sugary  fracture.  Ordinary 
limestone  is  one  of  our  most  important  building  ma- 
terials. 

Marble  is  capable  of  a  high  polish,  and  is  familiar  to 
all  in  the  form  of  table-tops,  mantels,  floors,  and  monu- 
ments. 

The  purest  and  finest  marble  is  used  in  sculpture,  and 
is  called  statuary  marble.  The  finest  qualities  come 
from  Carrara,  in  Italy,  and  from  the  Island  of  Paros, 
whence  the  celebrated  Parian  marble  of  the  Greek 
sculptors  takes  its  name. 

Many  ancient  temples  were  built  of  marble,  notably 
the  Parthenon  at  Athens.  The  capitol  at  Washington 
is  built  of  white  marble,  much  of  which  came  from  the 
quarries  at  Lee,  Massachusetts.  Excellent  marble  is 
found  abundantly  in  Vermont,  Western  Massachusetts, 
Eastern  New  York,  and  Western  Connecticut.  Berk- 
shire County,  Mass.,  rests  on  a  marble  and  limestone 
floor,  at  least  a  thousand  feet  in  thickness. 

Many  varieties  of  marble  are  beautifully  shaded, 
veined,  and  mottled. 

Chalk  is  a  soft  earthy  variety  of  limestone,  forming 
great  layers,  or  "strata,"  in  the  earth,  and  from  its  animal 


A    PIECE   OF   MARBLE.  135 

origin  and  structure  proving  of  even  more  interest  to 
the  geologist  than  to  the  mineralogist.  It  is  generally 
of  a  yellowish  tinge,  but  sometimes  of  snowy  whiteness. 
It  is  easily  broken,  has  an  earthy  fracture,  is  rough  to 
the  touch,  and  clings  slightly  to  the  tongue.  It  generally 
contains  a  little  silica,  alumina,  or  magnesia.  It  is 
sometimes  so  compact  as  to  be  available  for  build- 
ing. 

It  can  be  buried  into  quicklime,  and  nearly  all  the 
houses  in  London  are  cemented  with  mortar  made  of 
chalk. 

When  freed  from  its  particles  of  silica  by  pounding 
and  washing,  it  becomes  "whiting,"  familiar  to  every 
housewife.  Carpenters  and  others  use  it  for  making 
marks  which  are  easily  erased.  The  blackboard  with 
its  chalk  or  crayon  has  come  to  be  as  familiar  in  the 
lecture-room  of  the  university  as  in  the  humblest  village 
school. 

Calc-spar  is  the  crystallized  variety  of  calcite,  and 
it  occurs  in  several  hundred  shapes,  all  modifications  of 
the  rhombohedron,  which,  you  remember,  is  also  the 
regular  form  of  an  ice-crystal  (specimen  No.  22). 
This  represents  a  variety  very  abundant  at  Lock- 
port,  N.  Y.,  and  known  as  "dog-tooth  spar."  All 
varieties  of  calc-spar,  split  or  "cleave"  into  rhombohe- 
drons.  Transparent  specimens  have  the  property  of 
making  objects  viewed  through  them  appear  double. 
This  "  r^  jerty  is  called  double  refraction. 


136  THE   WORLD   OF   MATTER. 

QUESTIONS    ON    CHAPTER     12. 

1.  What  is  the  effect  of  hydrochloric  acid  upon  car- 
bonate of  lime? 

2.  What  is  the  chemical  composition  of  marble? 

3.  What  other  substances  have  the  same  composi- 
tion? 

4.  How  can  the  element  calcium  be  obtained?     De- 
scribe it. 

5.  What  effect  has  its  metal  upon  water? 

6.  How  can  marble  be  decomposed  without  acid? 

7.  What  are  the  properties  and  uses  of  lime? 

8.  Explain  the   Drummond  light. 

9.  What  is  litmus-paper? 

10.     What  is  calcite?     Name  several  varieties, 
n.     Why  is  the  carbonate   of  calcium  of  interest  to 
the  geologist? 

12.  What  is  chalk? 

13.  Describe  crystallized  calcite. 


CLAY.  137 


CHAPTER  XIII. 

CLAY. 

The  most  noticeable  substance  remaining  in  our  hand- 
ful of  earth,  now  that  we  have  removed  the  water, 
quartz,  charcoal,  and  limestone,  is  the  clay  that  we 
found  binding  these  substances  together. 

Clay  owes  its  origin  to  the  decomposition  of  minerals 
and  rocks,  and  is  rather  a  mixture  of  the  fine  particles  of 
other  disintegrated  substances  than  a  simple  mineral. 
We  shall,  therefore,  reserve  our  study  of  its  formation 
until  we  come  to  treat  of  geology,  but  it  is  of  present 
interest  to  us  on  account  of  the  decomposed  feldspar 
which  enters  largely  into  its  composition,  and  particularly 
on  account  of  the  metal,  aluminum,  which  next  to  silicon 
is  the  leading  element  in  this  feldspar.  Clay  is  essen- 
tially a  silicate  of  aluminum.  Clay  consisting  of  pure 
aluminum  silicate  is  called  kaolin. 

Clay  is  a  kind  of  soil  marked  by  smoothness  and 
stickiness,  or  "tenacity,"  and  by  the  fact  that  it  can  be 
''worked"  or  molded  into  any  desired  shape.  It  is  used 
by  sculptors  in  modeling  the  forms  which  are  after- 
ward to  be  cut  from  marble  or  cast  in  bronze.  On 
baking  it  becomes  as  hard  as  stone,  and  is  therefore  of 
great  value  for  the  manufacture  of  brick  and  tiles. 

The  various  forms  of  porcelain  and  earthenware  are 


138  THE   WORLD   OF  MATTER. 

made  of  baked  clay,  covered  with  some  substance 
which  melts  at  a  high  temperature,  and  forms  a  glaze 
or  enamel  binding  the  clay  together,  giving  it  a  smooth 
surface,  and  rendering  it  impervious  to  liquids  and  air, 
by  rilling  up  the  pores  which  abound  in  clay  baked 
without  an  enamel. 

For  the  manufacture  of  porcelain  the  finest  white  or 
china  clay  is  used,  while  for  common  earthenware 
colored  clays  may  be  used.  The  glaze  used  for  porce- 
lain is  usually  finely  powdered  feldspar.  For  ordinary 
earthenware,  a  "salt-glaze"  is  used.  This  is  made  by 
throwing  common  salt  into  the  furnaces  in  which  the 
ware  is  baking.  The  salt,  decomposed  by  heat,  causes 
a  deposit  of  fusible  silicate  upon  the  surface  of  the  clay. 

When  clay  becomes  firmly  compacted  it  becomes  slate. 

The  peculiar  clayey,  or  argillaceous  odor  of  slate  is 
enough  to  indicate  its  identity  with  clay,  even  if  we  did 
not  know  the  history  of  its  formation.  We  find  many 
degrees  of  hardness  in  clay.  It  sometimes  becomes 
very  hard  by  simple  drying,  as  we  often  see  in  dry 
weather,  but  this  is  not  slate,  and  no  amount  of  mere 
drying  will  convert  clay  into  slate,  for  dried  clay  when 
moistened  with  water  is  easily  brought  back  to  its  putty- 
like  or  plastic  state.  To  make  a  good  slate  the  hardening 
must  be  the  result  of  pressure,  as  well  as  dryness,  aided 
probably  to  some  extent  by  heat.  True  slate  is  a  per- 
manently hardened,  but  not  burnt  clay,  which  will  not 
become  soft  when  wet. 

Slate  is  easily  scratched  with  a  knife,  and  is  readily 
distinguished  from  limestone,  because  it  does  not  effer- 


CLAY.  139 

vesce  with  acid.  It  naturally  shows  the  same  varieties 
in  color  and  composition  as  clay.  A  good  assortment 
of  colors  is  afforded  by  the  roofing-slates.  Specimen 
No.  23  is  a  typical  slate,  for  it  not  only  has  a  compact 
structure,  and  an  argillaceous  odor,  but  it  is  very  plainly 
formed  in  layers,  or,  as  geologists  say,  it  is  distinctly 
stratified.  This  means  not  simply  that  it  splits  into 
leaves,  but  that  it  was  formed  by  the  deposition  of  lay- 
ers of  clay,  held  in  suspension  in  water.  Ordinary 
roofing-slates,  like  specimen  No.  24,  rarely  show  true 
stratification.  The  thin  layers  into  which  they  split 
have  been  developed  by  pressure  after  the  formation  of 
the  slate  by  deposition,  and  they  do  not  follow  the  lines 
of  the  real  stratification.  This  structure  is  known  as 
"slaty  cleavage."  Some  roofing  slates,  known  as  "rib- 
bon-slates," show  bands  of  various  colors  across  the  flat 
surfaces.  These  bands  indicate  the  lines  of  the  true 
bedding,  or  natural  layers  of  deposition. 

Slate  which  splits  easily  into  thin,  brittle  layers, 
parallel  with  the  bedding,  is  known  as  shale. 

We  must  now  consider  the  mineral  feldspar,  to  which 
the  origin  of  most  of  the  slates  and  clays  can  be  traced. 
It  must  be  borne  in  mind,  however,  that  feldspar  is  the 
name  of  a  group  of  minerals,  rather  than  of  any  one 
species.  Geologically,  the  feldspars  are  the  most  im- 
portant of  all  minerals  for  more  than  any  others,  with 
the  possible  exception  of  quartz,  they  enter  into  the 
composition  of  rocks,  which,  by  the  way,  are  large 
mixtures  or  aggregations  of  minerals,  no  single  crys- 
tal or  mineral-grain  being  properly  called  a  rock. 


140  THE   WORLD   OF   MATTER. 

The  abundance  of  the  feldspars  is  well  expressed  by 
the  name — feldspar  being  simply  the  German  for  field- 
spar,  and  implying  that  it  is  the  common  spar  or  min- 
eral of  the  fields. 

Like  clay,  the  feldspars  are  essentially  silicates  of 
aluminum,  with  the  addition  of  smaller  quantities  of 
other  elements. 

Their  general  characteristics,  including  easy  cleavage 
in  two  directions  at  right  angles  to  each  other  or  nearly 
so,  are  well  exhibited  in  the  common  variety,  orthoclase, 
specimen  No.  25. 

This  is  the  most  abundant  of  all  minerals,  forming 
the  principal  part  of  granite,  gneiss,  and  many  other 
important  rocks.  Its  most  common  colors  are  white, 
gray,  pink,  and  flesh-red. 

You  may  determine  for  yourself  the  physical  prop- 
erties of  orthoclase,  and  we  will  postpone  to  a  later 
chapter  the  examination  of  other  varieties  of  feldspar. 

Orthoclase  is  a  silicate  of  aluminum  and  potassium; 
that  is,  it  is  composed  of  silicon,  oxygen,  aluminum, 
and  potassium,  its  chemical  formula  being  K3Al2Si6 

Q,.« 

The  metal  aluminum  cannot  readily  be  obtained  di- 
rectly from  feldspar  or  clay,  and  the  various  processes 
of  its  manufacture  are  too  complicated  to  be  explained 
in  detail.  In  general,  an  aluminum  sulphate  is  first 
formed  by  decomposing  clay  with  sulphuric  acid,  This 
sulphate  of  aluminum  is  then  combined  with  an  alka- 
line sulphate  to  produce  alum.  Then,  to  a  solution  of 
the  alum,  ammonia  is  added,  and  a  white  powder  settles 


CLAY.  141 

to  the  bottom  of  the  solution.  This  powder  on  being 
heated  becomes  pure  alumina,  which  is  a  compound  of 
aluminum  and  oxygen,  Al^Og,  and  is  the  only  oxide  of 
aluminum  known.  .  Finally,  this  alumina  is  mixed  with 
carbon,  and  subjected  to  the  action  of  a  powerful  cur- 
rent of  electricity,  which  separates  the  metal  aluminum 
from  the  oxygen.  The  apparatus  used  for  this  purpose 
is  known  as  the  Cowles  electric  furnace.  There  are 
other  processes  for  obtaining  this  metal,  but  this  is  one 
of  the  best  and  cheapest. 

The  cheap  production  of  aluminum  from  clay  is  one 
of  the  important  practical  problems  needing  to  be 
solved,  because  the  properties  of  this  metal  are  such  as 
to  render  it  of  great  value,  while  its  abundance  in 
its  natural  compounds  is  so  unlimited  that  nothing  but 
the  difficulty  and  expense  of  preparing  it  prevents  it 
from  taking  (for  many  purposes)  the  place  of  iron,  to 
which  in  some  respects  it  is  greatly  superior.  In  the 
first  place  it  is  but  little  more  than  one-third  as  heavy, 
its  specific  being  2.7,  while  that  of  iron  is  7.8;  more- 
over, it  has  a  beautiful  color  and  lustre  resembling  silver, 
and  it  does  not  easily  rust  or  tarnish  on  exposure  to  dry 
or  moist  air.  It  is  exceedingly  strong,  and  yet  is  so 
malleable  that  it  can  be  hammered  into  thin  sheets  and 
wrought  into  any  desired  form. 

A  slight  alloy  of  copper  has  been  found  to  add  yet 
more  to  its  toughness  and  strength.  Serious  drawbacks 
to  its  usefulness,  however,  are  its  liability  to  be  at. 
tacked  by  salt,  and  by  vegetable  acids,  the  difficulty  of 
soldering  it,  and  the  difficulty  of  working  its  hard  alloys. 


142  THE   WORLD   OF   MATTER. 

Alumina,  the  oxide  from  which,  as  we  have  seen, 
the  metal  aluminum  is  obtained,  occurs  crystallized 
in  nature  in  the  forms  of  corundum,  ruby,  and  sap- 
phire. 

Corundum  is  inferior  only  to  the  diamond  in  hard- 
ness. It  is  generally  of  a  dull  and  muddy  appearance, 
even  in  its  hexagonal  crystals. 

A  common  variety  is  emery,  which  is  universally 
known  from  its'  use  in  polishing  and  cutting  gems, 
metals,  and  glass. 

Ruby  and  sapphire  are  identical  except  in  color,  and 
are,  indeed,  varieties  of  corundum.  No  gems,  with 
the  possible  exception  of  the  diamond,  are  so  highly 
prized.  They  are  transparent  and  brilliant.  The  finest 
rubies,  which  are  as  red  as  fire,  are  found  in  Burmah 
and  Siam,  and  the  finest  sapphires,  of  an  exquisite  blue 
color,  come  from  Ceylon.  In  Burmah,  when  a  very 
fine  stone  is  found,  a  procession  of  officers  and  soldiers 
mounted  on  elephants  is  sent  to  receive  it.  One  of  the 
titles  of  the  king  of  Burmah  is  "Lord  of  the  Rubies." 
A  ruby  weighing  more  than  twenty  carats  is  commonly 
called  a  carbuncle.  A  perfectly  pure  crystal  of  corun- 
dum, transparent  and  colorless,  is  known  as  white 
sapphire,  and  has  been  mistaken  for  the  diamond. 

QUESTIONS    ON    CHAPTER    13. 

} 

1.  What  is  clay?     Its  uses? 

2.  Describe  slate,  and  its  origin. 

3.  Distinguish    between      the    "stratification"     and 
"cleavage"  of  clay. 


CLAY.  M 

4.  Describe  orthoclase.     Its  composition? 

5.  How   is  aluminum    obtained,  and    what   are   its 
properties  ? 

6.  Mention  and  describe  three  varieties   of   crystal- 
lized alumina. 


THE   WORLD   OF   MATTER. 


CHAPTER  XIV. 

POTASSIUM MICA. 

In  our  study  of  clay  we  learned  that  it  is  essentially 
a  hydrous  silicate  of  aluminum;  but  besides  silicon, 
oxygen,  hydrogen,  and  aluminum,  it  sometimes  con- 
tains another  element^  namely,  potassium. 

We  might  also  have  found  traces  of  potassium  in 
the  ashes  left  mingled  with  charcoal  by  the  burned 
sticks  and  roots,  for  when  vegetable  material  is  burned 
the  potassium  remains  behind,  chiefly  in  the  form  of 
potassium  carbonate.  When  wood-ashes  are  treated 
with  water,  the  potassium  carbonate  dissolves,  and  may 
be  obtained,  though  in  an  impure  state,  by  evaporating 
the  solution.  The  substance  thus  obtained  is  popularly 
called  potash,  or  pearl-ash.  Its  chemical  formula  is 
K2CO3. 

Treat  two  or  three  pounds  of  wood-ashes  with  water. 
Filter  the  solution  and  test  its  effect  upon  red  litmus- 
paper.  You  observe  its  strong  alkaline  reaction  in 
turning  the  red  paper  blue. 

Evaporate  the  solution  to  dryness,  collect  the  residue, 
and  heat  it  in  a  test-tube  with  a  little  hydrochloric  acid. 
The  gas  given  off  you  will  recognize  as  carbon  dioxide 
if  you  pass  it  into  clear  lime-water. 

The  metal   potassium   was  first   obtained  by  passing 


POTASSIUM—  MICA.  145 

a  strong  electric  current  through  caustic  potash,  HKO. 
It  is  now  prepared  by  heating  potash  and  carbon  to- 
gether to  a  high  temperature  in  an  iron  retort.  The 
carbon  and  the  oxygen  of  the  potash  combine  and 
escape  as  a  gas,  hydrogen  is  set  free,  and  the  metal 
potassium,  which  vaporizes  at  red  heat,  distils  over  after 
the  manner  of  water. 

The  preparation  of  this  metal  is  attended  with  many 
difficulties  and  extreme  danger,  and  should  not  be  at- 
tempted except  by  experts. 

When  obtained  in  its  pure  state,  potassium  is  a  bright, 
silver-white  metal,  light  enough  to  float  on  water,  and 
so  soft  that  it  can  be  easily  cut  with  a  knife.  It  rapidly 
absorbs  oxygen  when  exposed  to  the  air,  and  gradually 
becomes  converted  into  a  white  oxide. 

It  unites  with  the  oxygen  of  water  with  great  energy, 
setting  the  hydrogen  free,  and  igniting  it  at  the  same 
time  by  the  heat  evolved  by  the  combination.  The 
flame  of  hydrogen  thus  ignited  is  tinged  with  a  pecu- 
liar purple,  which  is  characteristic  of  potassium. 

In  consequence  of  these  properties  of  potassium  it 
cannot  be  kept  in  the  air,  but  must  remain  until  desired 
for  use  under  some  oil,  like  petroleum,  upon  which  it 
does  not  act.  Throw  a  small  piece  of  potassium,  not 
larger  than  a  pea,  upon  water.  Study  the  result  care- 
fully. 

You  may  recollect  that  in  our  study  of  niter  it  was 
incidentally  mentioned  that  niter  is  a  compound  of 
nitrogen,  with  oxygen  and  potash.  This  niter  or,  to 
speak  chemically,  potassium  nitrate,  KNO3,  is  largely 


C',       *>»• 


146  THE  WORLD  OF  MATTER. 

used,  you  remember,  in  the  manufacture  of  gun-powder 
and  fire-works. 

One  of  our  first  experiments  was  the  preparation  of 
oxygen  by  heating  together  oxide  of  manganese  and 
potassium  chlorate.  This  potassium  chlorate  may  be 
obtained  by  passing  chlorine  gas  through  a  hot  solution 
of  caustic  potash.  It  occurs  in  white  rhomboidal  crys- 
tals of  a  pearly  lustre,  has  a  cooling  taste,  and  fuses 
easily.  It  parts  so  readily  with  its  oxygen,  that  if  sub- 
stances with  a  strong  affinity  for  that  gas,  such  as  car- 
bon, sulphur,  or  phosphorus,  are  heated  with  it,  even  so 
slightly  as  by  friction,  they  combine  with  the  oxygen 
with  explosive  force.  Chlorate  of  potash  is  therefore  used 
in  the  manufacture  of  friction-matches,  together  with 
phosphorus  and  sulphur.  We  need  not  consider  now 
any  of  the  other  numerous  compounds  of  potassium. 
It  is  an  important  element,  and  widely  distributed  in 
nature,  though  always  in  the  form  of  some  compound, 
chiefly  in  the  various  feldspars. 

From  these,  however,  it  has  been  hitherto  impracti- 
cable to  separate  it  until  they  have  become  disintegrated 
to  clay,  and  until  it  has  been  taken  up  by  plants 
and  transformed  into  vegetable  tissues,  from  the  ashes 
of  which  we  can  dissolve  potash  as  we  have  seen,  and 
from  the  potash  finally  separate  the  potassium. 

In  the  soil  which  we  examined  with  a  microscope, 
we  found  besides  the  minerals  already  studied  a  quan- 
tity of  "thin,  scale-like,  and  glistening"  particles.  These 
are  flakes  of  mica,  and  although  so  different  in  appear, 
ance  are  of  nearly  the  same  chemical  composition  as  the 


POTASSIUM— MICA.  147 

feldspars.  Clay,  which  is  derived  from  feldspar, 
is  a  hydrous  silicate  of  aluminum  and  potassium. 
Mica  is  a  silicate  of  aluminum  and  potassium,  with 
the  frequent  [addition  of  small  quantities  of  other  ele- 
ments. 

Mica,  like  feldspar,  is  the  name  of  a  group  or  family 
of  minerals  consisting  of  several  species.  The  most  im- 
portant characteristics  of  this  group  are  its  remarkable 
cleavage,  parallel  with  the  basal  planes  of  the  crystals, 
the  wonderful  thinness  of  the  plates  into  which  it 
splits — sometimes  no  thicker  than  the  one  3oo,oooth 
part  of  an  inch — and  above  all  the  elasticity  of  these 
plates,  or  lamellce.  By  these  peculiarities  the  identifi- 
cation of  mica  is  rendered  easy  and  certain. 

Of  the  several  species  of  mica  only  two  need  be 
noticed  now,  muscovite  and  biotite,  specimens  26  and 
27.  Determine  for  yourself  the  physical  properties  of 
these  specimens. 

Muscovite  contains  a  much  larger  percentage  of  silica 
than  biotite,  a  much  smaller  proportion  of  iron  (some- 
times  none),  and  only  about  one  half  the  amount  of 
magnesia. 

The  colors  of  muscovite  are  light,  being  white,  gray, 
and  more  rarely  brown  and  yellow ;  those  of  biotite 
are  dark,  ranging  from  dark  green  to  black. 

Biotite  has  also  the  peculiar  property  of  showing  two 
different  colors  when  held  against  the  light,  if  the  speci- 
men is  turned  from  side  to  side.  This  property  is 
called  dichroism,  and  biotite  is  a  dichroic  mineral.  This 
is  not  true  of  muscovite.  After  feldspar,  mica  is  the 


148  THE   WORLD   OF  MATTER. 

most  common  and  abundant  silicate,  and  forms  a  large 
part  of  such  rocks  as  granite,  gneiss,  and  mica-schist. 
Its  use  instead  of  glass  in  stoves,  lanterns,  and  other 
places  where  there  is  great  heat,  is  familiar.  In  Si- 
beria, Peru,  and  Mexico,  where  plates  a  yard  in  diam- 
eter are  found,  mica  is  used  as  a  substitute  for  glass  in 
windows. 

Mica  sometimes  occurs  in  beautiful  rhombic  or  hex-" 
agonal  crystals. 

The  curious  fact  may  be  worth  noting  that  three  of 
the  substances  which  we  have  found  mingled  in  our 
handful  of  earth,  namely,  chalk,  charcoal,  and  clay, 
have  for  hundreds  of  years  been  somewhat  fantastically 
joined  together  as  emblematical  of  the  characteristics 
of  true  and  loyal  service,  representing  freedom,  fer- 
vency, and  zeal. 

'What  is  freer  than  chalk,"  runs  the  old  proverb, 
"the  slightest  touch  of  which  leaves  a  trace  behind  ? 
What  is  more  fervent  than  charcoal?  for  when  prop- 
erly heated  it  causes  the  most  obdurate  metals  to  yield. 
What  is  more  zealous  than  clay,  which  adheres  to 
everything  it  touches,  and  which  as  earth  brings  forth 
every  living  tree  and  herb?" 

We  certainly  cannot  contemplate  without  interest 
these  most  common  minerals,  when  we  consider 
their  inestimable  value  to  mankind ;  and  we  cannot  fail 
to  be  reminded  of  the  danger  of  condemning  anything 
as  worthless  from  its  external  appearance,  since  we 
have  seen  chalk  glorified  in  the  calcium  light,  and  in 
the  form  of  marble  preserving  the  beautiful  conceptions 


POTASSIUM— MICA.  149 

of  the  world's  most  famous  artists;  charcoal  turning 
night  into  day  when  set  in  the  electric  lamp,  and  excit- 
ing the  admiration  and  desire  of  mankind  when 
crystallized  in  the  diamond;  and  clay  yielding  as 
if  by  magic  now  the  bright  and  untarnished 
metal,  aluminum,  and  again  the  brilliant  and  ex- 
quisitely colored  crystals  of  the  sapphire  and  the 
ruby;  nor  should  we  forget  those  less  dazzling  but 
more  important  properties  of  these  substances  by  virtue 
of  which  they  have  contributed  more  than  any  others 
to  the  education  and  refinement  of  mankind:  the  chalk 
and  clay  giving  to  our  schools  and  colleges  their  crayons 
and  slates;  and  the  charcoal  furnishing  the  basis  of  the 
ink  which  renders  writing  and  printing  possible,  and  in 
the  form  of  graphite  giving  us  the  lead-pencil,  which  is 
even  more  powerful  than  the  pen.  These  products  are 
of  far  more  value  than  metals  or  gems,  for  "the  price 
of  wisdom  is  above  rubies." 

QUESTIONS  ON  CHAPTER    14. 

1.  Describe  potassium. 

2.  Uses  of  potash? 

3.  What  is  mica? 

4.  Describe  biotite. 

5.  Describe  muscovite. 


ISO  THE  WORLD   OF   MATTER. 


CHAPTER  XV. 

A    LUMP    OF    SALT. 

In  our  study  of  water  we  learned  that  it  has  the  power 
of  dissolving  a  great  many  substances,  and  we  noted 
particularly  the  fact  that  rivers  in  their  progress  to  the 
sea  carry  the  elements  of  salt,  enough  in  the  ag- 
gregate to  make  the  whole  ocean  briny.  Salt  is  so  uni- 
versally distributed  that  we  feel  almost  certain  that  a 
portion  of  it  is  contained  in  our  garden  soil,  although  we 
have  not  as  yet  detected  it  in  the  specimens  of  earth  which 
we  have  examined.  Let  us  make  a  special  search  for 
it.  It  has  long  been  known  that  many  substances  when 
strongly  heated  in  a  nearly  colorless  flame  impart  to 
the  flame  peculiar  colors  by  which  the  substance  heated 
may  be  recognized. 

In  order  to  test  this  the  wick  of  your  alcohol  lamp 
should  be  clean,  and  the  flame  should  give  little  light, 
being  yellow  only  at  the  tip. 

You  can  get  a  good  alcohol  flame  by  taking  a  clean 
wick,  doubling  it,  and  leaving  the  doubled  part  outside 
for  the  flame.  Fig.  25. 

If  the  flame  becomes  colored  by  particles  of  minerals 
falling  on  the  wick,  take  the  wick  out  and  double  it  at 
a  fresh  place. 

Take  a  small  grain  of  salt  between  the  tips  of  a  pair 


A   LUMP   OF  SALT. 


of  platinum-pointed  forceps,  or  on  a  small  loop  made  in 
the  end  of  a  piece  of  platinum  wire,  and  pass  it  up  and 

down  the  edge  of  the  blue 
part  of  the  alcohol  flame, 
moving  it  from  below  at  the 
side  of  the  wick  up  toward 
the  tip.  Notice  the  bright 
yellow  color  it  imparts  to 
the  flame.  This  peculiar 
yellow  flame  is  character- 
istic of  one  of  the  two  ele- 
ments contained  in  common 
sail,  namely  sodium,  and  is 
proof  of  the  presence  of 
that  element  in  some  form 
in  the  flame.  Now,  salt  is 
one  of  the  most  common 
compounds  of  sodium,  and 
if  our  specimen  of  soil  causes 
this  yellow  color  to  appear  in  the  flame  we  may  fairly 
infer  that  it  contains  more  or  less  salt. 

Try  it.  Clean  your  forceps  or  wire  and  hold  a  little 
of  the  earth  in  the  flame  just  as  you  held  the  salt.  Do 
you  see  the  same  yellow  color? 

We  shall  not  spend  much  time  in  studying  salt  as 
such,  for  our  main  purpose  just  now  is  to  get  at  the 
elements  of  which  it  is  composed.  We  will  notice, 
however,  its  familiar  and  peculiar  taste,  its  whiteness, 
its  fusibility,  and  the  great  ease  with  which  it  dissolves 
in  water.  It  crystallizes  in  transparent  cubes,  as  may  be 


Fig   25. 


i$2  THE   WORLD   OF  MATTE-R. 

seen  by  slowly  evaporating  a  gently  heated  solution. 
If  the  brine  is  heated  nearly  to  the  boiling  point,  and 
rapidly  evaporated  by  the  exposure  of  a  large  surface 
to  the  air,  the  crystals  are  very  small,  as  in  fine  table- 
salt.  The  cubical  form  even  of  these  little  crystals 
may  be  seen  under  the  microscope,  although  the 
crystals  of  table-salt  commonly  have  their  edges  rounded 
like  pebbles,  partly  from  rubbing  against  one  another, 
and  partly  from  being  partially  dissolved  by  moisture 
absorbed  from  the  air.  You  should  therefore  prepare 
fresh  crystals  for  examination. 

The  quantity  of  salt  used  for  food,  either  directly  as 
a  condiment,  or  indirectly  in  the  preservation  of  meats 
and  fish,  and  for  other  purposes  is  enormous.  It  has 
been  estimated  at  fifty  pounds  a  year  for  each  person  in 
the  United  States,  and  twenty-two  pounds  for  each  per- 
son in  Great  Britain.  The  coarser  qualities  of  salt  are 
mostly  made  from  sea-water  or  other  brines  by  a  natural 
process  of  evaporation.  The  finer  grades  result  from 
heating  the  brines  artificially. 

Salt  is  also  found  occurring  in  a  solid  form,  both  mas- 
sive and  crystallized,  and  is  then  known  as  rock  salt. 
It  is  white,  gray,  or  more  rarely,  owing  to  the  presence 
of  impurities,  red,  violet,  and  blue.  In  some  places  it 
occurs  in  mountainous  masses.  A  .hill  of  rock-salt  in 
Spain  is  500  feet  high.  The  island  of  Ormuz  in  the 
Persian  Gulf  is  formed  of  rock-salt.  The  Indus  river 
in  the  upper  part  of  its  course  forces  its  way  through 
hills  of  rock-salt,  which  rise  in  cliffs  100  feet  above  the 
water,  Salt  is  also  found  in  beds  deep  under  ground, 


A    LUMP   OF   SALT.  153 

and  is  obtained  by  mining.  No  less  than  twenty-three 
of  the  United  States  are  engaged  in  the  production  of 
salt.  New  York  and  Michigan  are  the  most  productive. 

As  an  essential  part  of  the  food  of  live-stock  salt  is  a 
necessity  upon  every  farm.  Instances  are  not  uncom- 
mon where  beasts  of  burden  have  died  from  lack  of  it. 

Milch  cows  need  a  daily  allowance  in  order  to  pre- 
serve the  sweetness  of  their  milk,  and  the  quality  of  the- 
fleece  of  sheep  depends  to  a  great  extent  upon  their 
having  a  sufficient  supply  of  salt. 

In  freezing-mixtures  salt  is  of  great  use,  large  quanti- 
ties being  used  in  the  manufacture  of  ice-cream. 

As  salt  is  the  source  from  which  soda  is  derived,  it  is 
really  the  basis  in  the  manufacture  of  soaps  and  glass. 
Other  chemical  products  are  the  chlorine  used  in  the 
bleacheries  and  hydrochloric  or  muriatic  acid. 

The  processes  for  the  production  of  the  metal  sodium 
from  salt  are  too  complicated  to  be  detailed  here,  but 
they  consist  in  first  decomposing  the  salt  by  means  of 
heating  it  with  sulphuric  acid,  which  results  in  the 
separation  of  hydrochloric  acid,  and  sodium  sulphate. 
Afterward  the  sodium  sulphate,  or  "salt-cake,"  as  it  is 
called,  is  heated  with  powdered  coal  and  reduced  to 
sodium  sulphide:  and  the  sodium  sulphide  is  converted 
into  sodium  carbonate  by  means  of  chalk  or  limestone 
with  which  it  is  heated  in  a  furnace  of  special  construc- 
tion. The  next  operation  consists  in  freeing  the  car- 
bonate of  sodium  from  its  impurities,  which  is  accom- 
plished by  dissolving  it  out  in  water,  and  then  evapo- 
rating the  water,  and  calcining  the  residue. 


154  THE   WORLD   OF   MATTER. 

The  carbonate  thus  obtained  is  popularly  known  as 
"soda-ash,"  and  is  manufactured  by  the  hundred 
thousand  tons  every  year  for  use  in  glass-making,  soap- 
making,  bleaching,  etc.  From  this  "soda-a$h"the  metal 
sodium  may  be  obtained  by  decomposing  it  with  an 
electric  current,  or  by  reducing  it  with  carbon. 

Sodium  is  a  very  light  metal,  its  specific  gravity  being 
0.97,  or  very  nearly  that  of  ice.  It  floats  upon  water,  and 
owing  to  its  affinity  for  oxygen  rapidly  decomposes  the 
water,  disengaging  the  hydrogen.  If  the  water  be  hot, 
or  be  thickened  with  starch,  the  globule  of  metal  be- 
comes so  hot  as  to  ignite  the  escaping  hydrogen. 

It  will  be  worth  your  while  to  procure  a  small  piece 
of  sodium,  not  only  that  you  may  become  familiar  with 
so  important  an  element  in  its  purity,  but  also  that  you 
may  observe  its  action  upon  water.  Sodium  is  a  silver- 
white  metal,  soft  at  ordinary  temperatures,  and  melting 
readily.  It  is  so  widely  distributed  in  natuie  that  there 
is  not  a  speck  of  dust  entirely  free  from  its  presence. 

QUESTIONS    ON  CHAPTER     15. 

1.  How  can  we  detect  the  presence    of    a    minute 
portion  of  salt  in  the  soil? 

2.  How  should  the  wick  of  an  alcohol  lamp  be  ar- 
ranged so  as  to  yield  a  nearly  colorless  flame? 

3.  What  color  does  salt  or  sodium  impart  to  flame? 

4.  Describe  the  physical  properties  of  common  salt. 

5.  What  is  the  form  of  its  crystals? 

6.  How  and  where  is  it  obtained? 

7.  Its  uses? 


A   LUMP   OF  SALT.  155 

8.  Give  an  outline   of   the   process   for   procuring 
sodium  from  salt. 

9.  Uses  of  carbonate  of  soda? 

10.  Describe  the  metal  sodium. 

11.  Its  effect  upon  water. 

12.  Its  distribution. 


156  THE   WORLD   OF  MATTER. 


CHAPTER  XVI. 

MURIATIC  ACID. 

In  the  preceding  chapter  we  incidentally  learned  that 
the  first  step  in  the  process  of  separating  the  metal  sodi- 
um from  common  salt  is  the  addition  of  sulphuric  acid 
to  the  salt;  and  we  further  learned  that  this  acid  causes 
the  formation  of  hydrochloric  acid  and  sodium  sulphate. 
We  then  neglected  the  hydrochloric  acid  and  followed 
the  further  treatment  of  the  sodium  sulphate,  from 
which  we  finally  obtained  the  metal  sodium. 

Let  us  now  consider  the  hydrochloric  acid.  In  the 
first  place  we  must  make  enough  to  study.  This  is  a 
very  simple  matter.  Pour  half  a  teaspoonf ul  of  strong 
sulphuric  acid  on  a  few  grains  of  common  salt  in  a  test 
tube.  What  takes  place  ?  What  is  the  appearance  of  the 
gas  that  is  given  off?  This  gas  is  hydrochloric  acid;  the 
substance  remaining  in  the  tube  is  sodium  sulphate. 

Hydrochloric  acid  in  the  form  of  gas  is  very  readily 
absorbed  by  or  dissolved  in  water,  just  as  ammonia  gas 
is,  and  the  hydrochloric,  or  "  muriatic,"  acid  of  the  drug 
stores  is  merely  water  saturated  with  this  gas. 

The  popular  name,  "muriatic,"  is  derived  from  the 
Latin,  muria,  meaning  brine,  and  refers  to  its  production 
from  salt. 

Make  the  following  experiment,  and  you  will  obtain 


MURIATIC  ACID. 


157 


a  plentiful  supply,  both  as  a  gas  and  in  the  liquid  solution. 
Arrange  apparatus  as  in  Fig.  26. 


Fig.  26. 

Weigh  out  separately  100  grains  of  common  salt,  100 
grains  of  concentrated  sulphuric  acid,  and  one  part  of 
water.  Mix  the  acid  and  water,  taking  the  precaution 
already  noted  of  pouring  the  acid  in  very  slowly  while 
the  mixture  is  constantly  stirred.  Let  the  mixture  cool 
and  then  pour  it  upon  the  salt  in  the  flask.  Now  heat 
the  flask  gently  over  an  alcohol  lamp  or  a  gas-jet,  and 
the  gas  will  be  regularly  given  off.  Conduct  it  at  first 
through  two  or  three  double-necked,  or  "Wolff's 
bottles,"  until  what  passes  over  is  completely  absorbed  in 
the  first  Wolff's  bottle.  This  is  to  get  rid  of  the  air. 
At  first  a  bubbling  occurs  in  all  the  bottles  as  the  air  in 
the  apparatus  is  being  driven  out.  When  the  air  has 
all  been  expelled,  the  bubbling  ceases  and  the  hydro- 
chloric gas  is  all  absorbed  in  the  water  in  the  first  bottle. 


THE  WORLD   OF  MATTER. 


After  the  gas  has  passed  for  ten  or  fifteen  minutes,  you 
may  disconnect  the  tube  at  A.  Notice  the  fumes. 
Breathe  upon  them  and  observe  that  they  become  more 
dense.  Apply  a  lighted  match  to  the  escaping  gas. 


Fig.  27. 


Does  it  burn?  Collect  some  of  the  gas  in  a  dry  jar  or 
cylinder  by  letting  the  delivery  tube  extend  to  the  bot- 
tom of  the  jar,  and  covering  its  mouth  with  a  piece  of 
paper.  Fig.  27. 


MURIATIC  ACID.  159 

The  specific  gravity  of  the  gas  being  greater  than  that 
of  air,  the  jar  must,  of  course,  have  its  mouth  upward. 
Has  the  gas  any  color?  Is  it  transparent?  Insert  a  burn- 
ing taper  in  the  jar.  Does  the  gas  support  combustion? 

Now,  connect  the  generating-flask  again  with  the 
bottles  containing  water,  and  let  the  process  continue 
until  no  more  gas  comes  over.  What  substance  remains 
in  the  flask? 

You  now  have  in  your  first  Wolff's  bottle  ordinary 
hydrochloric  acid  in  solution,  and  you  may  test  it  as 
follows:  Put  a  little  granulated  or  chipped  zinc  into  a 
test-tube  and  pour  some  of  the  solution  upon  it. 

By  applying  a  match  to  the  resulting  gas,  you  will 
recognize  it  as  hydrogen,  which,  you  recollect,  we  have 
previously  obtained  by  the  action  of  hydrochloric  acid 
upon  zinc. 

Add  ten  or  twelve  drops  of  the  solution  to  a  teaspoon- 
ful  of  water  in  a  glass.  Taste  the  dilute  solution. 
How  would  you  describe  the  taste? 

Dip  a  piece  of  blue  litmus-paper  into  the  solution. 
What  is  the  effect? 

These  tests  are  sufficient  to  indicate  that  th'3  solution 
contains  hydrochloric  acid,  HC1,  which  is  a  compound 
of  hydrogen  and  a  new  element  called  chlorine.  This 
element  we  will  next  endeavor  to  separate  from  the 
hydrochloric  acid  for  our  examination. 

QUESTIONS    ON    CHAPTER     l6. 

i.  How  can  hydrochloric  acid  be  obtained  from 
common  salt? 


160  THE  WORLD  OF  MATTER. 

2.  What  substance  is  left  behind? 

3.  How  do  we  obtain  hydrochloric  acid  in  a  liquid 
form? 

4.  What  is  a  "Wolff's  bottle?" 

5.  How  may  we  recognize  hydrochloric  gas? 

6.  Describe  it.  j 

7.  What  is  its  composition? 

8.  What  is  the  derivation  and  meaning  of  the  word, 
"muriatic?" 


CHLORINE.  16! 


CHAPTER  XVII. 

CHLORINE. 

In  order  to  separate  the  chlorine,  Cl,  from  hydro- 
chloric acid,  HC1,  it  is  obviously  necessary  merely  to 
remove  the  hydrogen  from  it.  This  can  readily  be  done 
by  adding  to  the  acid  some  substance,  such  as  oxygen, 
which  has  a  stronger  attraction  for  the  hydrogen,  than 
the  chlorine  has.  The  most  convenient  substance  in 
practice  is  manganese  dioxide,  which  we  have  already 
handled  when  we  were  preparing  oxygen.  When 
brought  together  with  hydrochloric  acid,  the  manganese 
dioxide  parts  readily  with  its  oxygen,  the  oxygen  unites 
with  the  hydrogen,  and^part  of  the  chlorine  is  set  free. 
The  reaction  is  represented  thus: 

MnO2     +    4HC1     :         MnCl2     +    2H2O     +    2C1. 

This  method  is  too  expensive  to  be  used  in  the  manu- 
facture of  chlorine  in  the  immense  quantities  required 
for  commerce,  and  cheaper  processes  have  been  devised, 
with  which,  however,  we  are  not  now  concerned.  We 
will,  therefore,  use  the  manganese  dioxide  as  follows: 
Put  into  a  flask  three  or  four  ounces  of  black  oxide  of 
manganese.  Pour  upon  it  enough  ordinary  concen- 
trated hydrochloric  acid  to  cover  it  completely.  Ar- 
range the  apparatus  as  shown  in  Fig.  27,  on  page 


162  THE   WORLD   OF   MATTE&. 

158,  except  that  in  order  to  secure  a  very  gentle  heat, 
the  flask  may  be  set  in  a  pan  of  sand  over  the  flame. 

Heat  very  gently,  and  collect  six  or  eight  dry  cylin- 
ders or  bottles  full  of  chlorine  in  trie  same  manner  as 
described  in  the  preceding  chapter  for  collecting  hydro- 
chloric gas. 

You  can  see  when  the  vessels  are  full  by  the  color  of 
the  gas.  The  oxide  of  manganese  used  for  this  experi- 
ment should  be  in  the  form  of  small  lumps  free  from 
powder.  This  experiment,  like  all  others  concerned 
with  chlorine,  should  be  carried  on  in  a  place  well  venti- 
lated by  a  strong  draft,  as  by  an  open  fire-place,  under 
a  metal  hood  connected  with  a  chimney,  or  out  of  doors. 
Do  not  breathe  any  of  the  gas. 

You  may  now  proceed  to  study  the  chlorine  you  have 
collected.  You  observe  that  it  is  greenish-yellow. 
Notwithstanding  the  precaution  of  having  a  good 
draught,  you  will  probably  perceive  that  it  has  a  dis- 
agreeable odor,  and  that  it  irritates  the  passages  of  the 
throat  and  nose.  The  feeling  produced  is  like  that 
caused  by  a  cold  in  the  head.  Inhaled  in  concentrated 
form  it  would  cause  death.  It  is  more  than  twice  as 
heavy  as  air. 

Into  one  of  the  jars  of  chlorine  introduce  a  little  finely 
powdered  antimony.  The  two  elements  at  once  com- 
bine with  light  and  heat,  somewhat  as  iron  burns  with 
oxygen. 

Into  a  second  jar  introduce  a  few  pieces  of  heated 
copper  foil.  They  burn  brilliantly,  and  form  a  copper 
chloride. 


CHLORINE.  163 

Into  a  third  jar  drop  a  piece  of  paper  written 
on  with  ink,  some  flowers,  and  some  pieces  of  colored 
calico,  all  moistened.  Most  of  the  colors  will  be  de- 
stroyed. 

In  the  fourth  jar  drop  a  dry  piece  of  the  same  calico. 
It  is  not  bleached. 

This  bleaching  power  of  chlorine  is  of  enormous  im- 
portance in  the  cotton  and  paper  trades.  It  does  not,  as 
a  rule,  act  upon  mineral  colors,  nor  the  black  tints  pro- 
duced by  carbon.  Test  this  by  placing  a  piece  of 
printed  paper  in  a  jar  of  chlorine.  The  print  is  not 
affected. 

The  bleaching  properties  of  chlorine  depend  upon  its 
power  of  combining  with  the  hydrogen  of  water  and 
liberating  the  oxygen,  which  then  oxidises  or  burns  up 
the  coloring  matters. 

Besides  this  property  chlorine  is  also  useful  as  a  dis- 
infectant, and  is  largely  used  in  destroying  bad  odors 
and  the  poisonous  germs  of  disease,  although  this  effect 
is  probably  produced  also  by  liberated  oxygen,  rather 
than  by  direct  action  of  the  chlorine. 

Chlorine  can  be  combined  directly  with  hydrogen  to 
produce  hydrochloric  acid.  If  equal  volumes  of  these 
two  gases,  hydrogen  and  chlorine,  be  mixed,  no  combi- 
nation occurs  so  long  as  the  mixture  remains  in  the  dark 
and  at  the  ordinary  temperature;  but  if  the  mixed  gases 
be  exposed  to  sunlight,  or  if  a  flame  be  applied,  or  an 
electric  spark  passed  through  them.,  a  sudden  combina- 
tion occurs,  and  the  heat  evolved  produces  a  violent  ex- 
plosion. 


164  THfi  WORLD  OF  MATTER. 

Copper,  mercury,  tin,  platinum,  silver,  iron,  and  cer- 
tain other  metals  unite  very  readily  with  chlorine  form- 
ing chlorides.  The  well-known  substance,  "  chloride  of 
lime,"  is  formed  by  passing  chlorine  into  slaked  lime. 

QUESTIONS    ON    CHAPTER     1 7. 

1.  How   can   hydrochloric   acid    be    analyzed    into 
chlorine  and  hydrogen? 

2.  What  precautions  must  be  taken  in  dealing   with 
chlorine  ? 

3.  Describe  the  gas,  its  color,  smell,  and  effects. 

4.  What  is  the  effect  of  introducing  powdered  anti- 
mony into  chlorine? 

5.  How  does  heated  copper  foil  act  with  chlorine? 

6.  What  effect  has  chlorine  upon  colored  fabrics? 

7.  Explain  the  reason  for  the  bleaching  power  of 
chlorine. 

8.  What  colors  are  not  affected  by  it  ? 

9.  Explain  its  power  as  a  disinfectant. 

10.  What  occurs  when  chlorine  and   hydrogen  are 
mixed? 

11.  What  is  chloride  of  lime? 


IRON.  165 


CHAPTER  XVIII. 

IRON. 

We  have  now  accounted  for  everything  we  observed 
in  our  handful  of  soil,  but  before  leaving  it  let  us  look 
again.  Take  another  handful  and  wash  it  carefully  in 
a  bowl  of  water,  pouring  off  the  muddy  water  and  add- 
ing  clear  water  until  we  obtain  clean  sand.  Unless 
your  soil  differs  from  mine  you  will  be  able  to  find 
among  the  grains  of  quartz  which  make  up  most  of 
this  sand,  other  grains  of  a  black  color,  some  of  which 
are  attracted  by  a  magnet.  These  grains  are  a  kind  of 
iron  ore. 

When  clay  or  soil  is  burned,  as  in  making  brick, 
the  red  color  produced  is  an  evidence  of  the  presence  of 
iron.  Compare  the  red  color  of  bricks  with  the  red 
rust  seen  on  iron  which  has  been  strongly  heated. 
You  may  also  remember  that  in  speaking  of 
mica,  I  told  you  that  besides  silica,  aluminum,  and 
potassium,  it  usually  contains  a  little  iron.  It  is  to 
a  trace  of  iron  also  that  we  must  attribute  the  brown 
color  which  we  found  tingeing  some  of  the  grains  of 
quartz  which  we  examined  under  the  microscope. 

Before  reading  further  call  to  mind  all  that  you  al- 
ready know  about  this  element.  By  its  lustre  and  hard- 
ness, and  malleability,  you  recognize  it  as  a  rqetal.  You 


166  THE   WORLD   OF   MATTER. 

distinguish  it  easily  from  most  other  metals,  such  as  gold, 
s  Iver,  lead,  and  tin,  by  its  dark  color,  its  hardness,  and 
the  reddish  rust  or  oxide  which  so  quickly  gathers  on 
its  surface  when  exposed  to  the  weather. 

You  are  familiar  with  the  properties  which  make  iron 
by  far  the  most  useful  metal  in  the  world.  You  know 
that  it  can  be  had  in  three  common  forms,  wrought-iron. 
cast-iron,  and  steel;  that  wrought  or  worked  iron  is  the 
softest  form  and  is  nearly  pure  iron.  It  is  used  when 
we  require  strength  and  toughness  without  stiffness  or 
elasticity ;  as  for  horse  shoes,  nails,  wire,  chains,  boilers, 
and  bridges. 

Steel,  you  know,  is  the  hardest  form  of  iron.  It  is 
not  so  pure  as  wrought-iron,  but  contains  a  certain  ad- 
mixture of  carbon,  though  not  so  much  as  there  is  in 
cast-iron. 

It  is  used  when  to  the  greatest  strength  we  would  add 
hardness  and  elasticity,  and  is  peculiarly  suitable  for 
tools,  springs,  rails,  wire,  and  the  finer  parts  of  ma- 
chinery. What  could  take  the  place  of  steel  in  the 
manufacture  of  needles? 

Cast-iron  is  less  pure  than  steel,  and  is  brittle.  It  is 
used  where  rigidity  of  form,  without  elasticity  or  flexi- 
bility or  malleability,  is  desired.  It  melts  at  less  heat 
than  wrought-iron  or  steel,  and  can  readily  be  poured 
into  moulds.  It  is  used  for  stoves,  furnaces,  cooking 
utensils,  tubing,  and  the  framework  of  machinery. 

One  of  the  most  valuable  properties  of  iron  is  that  at 
a  red  heat  it  becomes  soft  like  wax,  in  which  condition 
two  pieces  strongly  pressed  together  unite,  and  become 


IRON.  167 

one    continuous    piece.     This   process  is  called    weld- 
ing. 

Another  property  of  iron,  and  one  by  which  it  can 
be  instantly  detected,  is  its  sensitiveness  to  the  attraction 
of  a  magnet,  and  its  power  of  becoming  magnetic 
during  the  passage  of  an  electric  current.  A  bar  of 
steel  becomes  permanently  magnetised  when  it  is  rubbed 
by  a  magnet.  To  this  property  of  steel  we  owe  the 
"mariner's  compass,"  which  guides  our  ships  and  steam- 
ers across  the  sea;  while  to  the  temporary  magnetism 
produced  in  soft  iron  by  the  passage  of  a  current  of  elec- 
tricity, we  owe,  among  other  things,  the  telegraph,  the 
telephone,  and  the  "dynamo"  or  electric  engine,  which 
gives  us  the  electric  motor  and  the  electric  light. 

Pure  metallic  iron  is  not  found  in  nature,  except  in 
small  quantities  in  Greenland  in  a  rock  supposed  to  have 
been  thrown  out  of  the  earth  by  a  volcano;  and  in 
meteorites.  It  is  a  white  metal  with  a  strong  lustre. 
Iron  is  usually  found  in  combination  with  oxygen,  with 
oxygen  and  carbon,  or  with  sulphur. 

The  three  principal  oxides  of  iron  (specimens  Nos.  10, 
1 1 ,  and  1 2)  are  known  as  limonite,  hematite,  and  magnetite. 
The  history  of  the  formation  of  these  ores  through  the 
agency  of  vegetable  matter  is  most  interesting,  but  will 
more  properly  be  given  when  we  come  to  the  study  of 
geology.  They  are  easily  distinguished  from  one 
another  by  the  colors  of  their  powders,  and  by  the  mag- 
netism of  magnetite,  and  they  may  be  known  from  all 
other  common  rocks  by  their  high  specific  gravity. 
Magnetite  is  the  richest  in  iron,  and  limonite  the  poorest. 


168  THE  WORLD   OF  MATTER. 

The    carbonate    of     iron  is   called    siderite*   FeCO, 

'  o 

Its  crystallization  and  cleavage  are  essentially  like  calcite. 
Test  for  yourself  its  other  physical  properties. 

Iron  combined  with  sulphur  forms  iron  sulphide, 
FeS2,  known  by  mineralogists  as  iron  pyrites,  or  py rite. 
(Specimen  No.  29.)  It  is  usually  found  in  brilliant  yel- 
low cubical  crystals,  although  there  is  also  a  twelve- 
sided  form,  and  is  frequently  mistaken  by  the  ignorant 
for  gold.  It  has  therefore  been  called  "  Fool's  gold." 
It  may  easily  be  distinguished  from  gold  by  its  brittle- 
ness  and  hardness,  which  is  so  great — nearly  7 — that  it 
will  strike  fire  with  steel.  Hence  the  name,  pyrite  or 
fire-stone. 

When  heated  in  a  closed  tube  sulphur  is  given  off. 
Verify  this  statement  -by  experiment,  and  test  the  dark 
colored  residue  by  a  magnet. 

The  extraction  of  iron  from  its  ores  consists  in  first 
converting  the  ore  into  an  oxide  of  iron,  unless  the 
oxides  themselves  are  used.  This  is  accomplished  by 
roasting  them.  If  sulphides  are  roasted  the  sulphur 
passes  off  as  sulphur  dioxide,  and  iron  oxide  remains. 

The  next  step  is  the  reduction  of  the  oxides  by  heat- 
ing them  with  carbon  in  the  form  of  charcoal  or  coke. 
For  this  purpose  the  ore  and  carbon  are  mixed  and 
heated  in  a  blast-furnace,  constructed  of  fire-brick  and 
masonry.  Alternate  layers  of  ore  and  fuel  are  intro- 
duced. Limestone  or  quicklime  is  also  added  as  zflux. 
The  object  of  this  is  to  form  a  fusible  substance  with 
the  earthy  part  of  the  ore.  As  the  heat  increases  the 
ore  and  flux  melt  together,  but  the  iron  being  the 


IRON. 


169 


heavier  liquid  sinks  to  the  bottom,  whence  it  is  drawn 
off  into  proper  receptacles,  after  which  the  melted  flux 

with  its  impurities  is  al- 
lowed to  escape.  This 
refuse  is  called  slag. 

The  iron  drawn  off 
from  the  furnace  is  called 
pig-iron.  It  is  impure, 
containing  phosphorus, 
sulphur,  silicon,  and  from 
2  to  6  per  cent,  of  carbon. 
It  is  used  for  cast-iron. 
Cast-iron  is  converted 
into  wrought-iron  in  one 
of  two  ways:  (i)  By 
melting  it  and  blowing 
air  into  the  molten  mass. 
The  carbon,  phosphorus, 
and  silicon  are  thus  oxi- 
dized and  removed.  This 
process  is  known  as  pud- 
dling. 

(2)  By  mixing  cast-iron  with  some  of  the  purer  ores, 
and  heating  to  a  high  temperature,  when  the  carbon, 
phosphorus,  and  silicon  are  oxidized  by  the  oxygen  of 
the  ores.  This  process  is  called  cementation. 

Steel  contains  from  I  to  2  per  cent,  of  carbon.  There 
are  two  ways  of  making  steel: 

(i)  Wrought-iron  is  heated  with  charcoal,  or  with 
other  iron  containing  carbon. 


Fig.  27M- 


iyo  THE  .WORLD   OF   MATTER. 

(2)  Cast-iron  is  melted  in  a  large  vessel,  and  is  then 
partly  oxidized  by  currents  of  air  forced  into  the  mass. 
Cast-iron  is  now  added,  and  steel  containing  any  desired 
proportion  of  carbon  is  thus  made.  This  is  known  as 
the  Bessemer  process. 

QUESTIONS    ON    CHAPTER    iS. 

1.  Describe  cast-iron. 

2.  Describe  steel. 

3.  Describe  wrought-iron. 

4.  State  the  uses  of  each. 

5.  What  is  the  color  of  pure  iron? 

6.  What  are  the  three  principal  oxides  of  iron? 

7.  Describe  siderite. 

8.  What  is  iron  pyrites? 

9.  How  may  it  be  distinguished  from  gold  ? 

10.  How  is  iron  extracted  from  its  ores? 

11.  How  is  wrought-iron  made ? 

12.  How  is  steel  made? 


BY   WAY   OE  REVIEW.  171 


CHAPTER  XIX. 

BY    WAY    OF    REVIEW. 

We  have  now  reached  a  point  in  our  study  of  the 
world  of  matter  where  it  will  be  profitable  for  us  to  rest 
for  a  time,  and  take  a  bird's-eye  view^of  the  path  along 
which  we  have  been  advancing. 

We  began  with  a  piece  of  ice,  because  that  was  as 
handy  a  specimen  as  we  could  think  of,  and  one  with 
which  we  were  already  familiar. 

Having  observed  its  physical  properties,  such  as  hard- 
ness, transparency,  and  weight,  we  were  especially  in- 
terested in  the  change  which  was  caused  in  its  structure 
by  the  heat  of  the  hand,  /.  £.,  its  melting. 

This  led  us  to  various  experiments  by  which  we 
studied  the  phenomena  connected  both  with  the  melting 
of  ice  and  the  freezing  again  of  water,  including  the 
peculiarities  of  its  crystallization. 

Having  melted  our  ice  we  proceeded  to  examine  the 
water  produced  thereby,  and  discovered  first  its  property 
of  dissolving  other  substances;  incidentally  learning 
something  of  capillary  .attraction,  that  combination  of 
ordinary  forces  which  results  in  lifting  a  liquid  through 
minute  tubes  or  pores.  We  next  tried  the  effect  of  a 
greater  degree  of  heat  upon  water,  and  found  that  at 
212  degrees  Fahrenheit  it  begins  to  be  converted  into 


172  THE   WORLD   OF   MATTER. 

an  invisible  vapor  called  steam,  a  process  which  is  ac- 
companied by  a  violent  agitation  and  bubbling,  known 
as  boiling,  or  ebullition;  and  we  learned  that  on  the 
withdrawal  of  heat  this  vapor  is  again  condensed  in  the 
form  of  water.  Observing  that  ice,  water,  and  steam 
are  riot  different  substances,  although  apparently  so 
unlike,  we  were  curious  to  ascertain  what  it  is  that  gives 
a  substance  its  identity;  or  in  other  words,  to  learn 
what  constitutes  a  simple  element.  We  found  that 
those  substances  are  considered  elementary  which  have 
never  been  resolved  into  simpler  substances,  and  that 
for  a  long  time' it  was  supposed  that  the  elements  were 
four,  namely,  water,  air,  fire,  and  earth.  This  led  us 
to  examine  water  more  carefully,  and,  on  testing  it 
with  an  electric  current,  we  found  that  it  separated  into 
the  two  gases,  oxygen  and  hydrogen.  As  these  could 
not  be  further  analyzed  we  concluded  that  they  are 
elements. 

In  Chapter  V,  we  studied  the  oxygen  and  hydrogen 
we  had  obtained  from  the  water,  and  learned  many 
important  facts  regarding  chemical  combinations,  and 
particularly  that  sort  of  combination  accompanied  by 
heat  and  light  which  is  called  combustion. 

In  this  connection,  having  observed  that  there  is  a 
strong  resemblance  between  our  ordinary  fires  and  the 
flames  which  are  produced  by  burning  substances  in 
oxygen,  we  examined  a  portion  of  the  air  which  feeds 
our  common  fires,  and  found,  as  we  had  suspected,  that 
it  is  largely  made  up  of  oxygen.  Our  curiosity  to  know 
why  the  oxygen  of  the  air  does  not  burn  up  everything 


fcY   WAY   OF  REVIEW.  173 

in  the  world  brought  us  to  the  discovery  that  nitrogen, 
a  powerful  extinguisher  of  fire,  is  mingled  in  the  air 
with  the  oxygen,  and  we  afterward  found  this  ap- 
parently inert  nitrogen  combined  with  other  elements 
.and  forming  highly  explosive  compounds  like  gun- 
powder and  nitro-glycerine;  we  also  found  it  constitut- 
ing a  large  proportion  of  the  food  of  animals. 

Remembering  the  old  notion  that  earth  is  an  elemen- 
tary substance,  and  knowing  that  that  could  not  be 
true,  since  we  had  learned  that  at  least  three  different 
elements,  namely,  oxygen,  hydrogen,  and  nitrogen, 
enter  into  its  composition,  we  determined  to  examine 
with  some  care  a  handful  of  earth  from  the  garden.  In 
this  we  found — besides  the  hydrogen  and  oxygen  of 
water — quartz,  limestone,  charcoal,  and  clay,  including 
its  aluminum,  and  potassium ;  and  about  each  of  these, 
in  passing,  we  gleaned  such  information  as  was  at  hand. 
Then,  by  the  aid  of  its  yellow  flame,  we  discovered  a 
little  salt  in  the  soil,  and  traced  it  to  its  elements, 
sodium  and  chlorine,  and  finally  we  found  a  trace  of 
iron. 

Our  course  has  not  been  a  strictly  scientific  one,  per- 
haps, inasmuch  as  science  busies  itself  largely  with  ar- 
ranging the  subjects  of  its  consideration  in  groups  or 
classes  according  to  certain  resemblances  which  exist 
between  them — as,  for  example,  when  the  zoologist 
groups  all  animals  that  have  back-bones,  under  the 
name  vertebrate — while  we  have  taken  our  specimens  in 
the  order  suggested  by  convenience  and  natural  asso- 
ciation. A  science,  too*,  walks  within  well-defined 


174  THE  WORLD  OF  MATTER. 

bounds,  closing  its  eyes  for  the  time  to  everything  out- 
side its  own  narrow  lines,  in  order  that  it  may  be  more 
certain  of  seeing  clearly  and  comprehensively  every- 
thing within  those  lines;  while  we  have  not  hesitated 
to  leap  over  the  fence  every  now  and  then,  whenever 
anything  of  interest  appeared  in  the  fields  that  bordered 
our  pathway.  We  have  been  taking  a  ramble  along 
the  brooks,  and  through  the  fields,  rather  than  working 
methodically  in  a  laboratory  or  museum. 

It  will  be  no  hindrance,  however,  to  our  progress  in 
science  that  we  have  thus  pleasantly  gathered  and 
studied,  even  though  apparently  at  random,  a  goodly 
collection  of  mineral  specimens,  before  undertaking  to 
make  any  systematic  classification. 

In  fact,  there  seems  to  be  something  absurd,  or  at 
least  unnatural,  in  that  method  of  studying  natural 
science  which  begins  by  committing  to  memory 
the  classified  results  of  the  labors  of  great  scientists, 
instead  of  following  their  example,  by  first  collecting 
our  material  and  afterward  learning  how  to  arrange  it. 

One  of  the  chief  disadvantages  of  the  ordinary 
method  of  acquiring  a  knowledge  of  nature  by  the 
routine  of  definition  learning  and  system  memorizing 
is  that  in  that  way  we  get  our  information  in  narrow 
and  artificial  fragments,  and  lose  sight  of  the  intimate 
natural  relations  that  exist  between  all  the  sciences,  and 
fail  to  comprehend  that  all  science  or  knowledge  is  es- 
sentially one.  Thus  it  often  happens  that  we  hear  a 
young  student,  who  has  read  a  certain  chemical  text- 
book, remark  that  he  has  "finished  chemistry,  and  is 


fcY  WAY   OP  REVIEW.  175 

about  to  take  up  mineralogy ;"  and  I  have  even  known 
persons  who  thought  they  had  mastered  geology  when 
they  had  learned  the  names  and  characteristics  of  the 
several  geologic  strata,  although  they  were  quite 
ignorant  of  the  chemical  composition  of  the  most  com- 
mon minerals,  and  knew  nothing  at  all  of  plant  or 
animal  life  and  structure. 

Our  work  has  not  been  in  vain  if  we  have  learned 
the  central  truth  that  all  the  various  sciences  are  not 
only  interdependent,  but  are  all  merely  parts  of  one 
harmonious  whole,  so  that  no  one  can  be  said  to  have 
"finished"' any  one  science  until  he  is  master  of  all 
science.  Those  students  who  are  seeking  for  new  facts 
with  a  view  to  increasing  the  world's  knowledge  do 
well  to  confine  their  investigations  closely  within  spec- 
ial and  narrow  lines ;  and  on  this  principle  a  "special- 
ist" merits  praise  for  devoting  his  whole  life  to  the  study, 
it  may  be,  of  one  family  of  spiders,  even  though  he 
may  never  allow  himself  to  notice  a  butterfly,  a  bird, 
a  crystal,  a  tree,  a  mountain,  or  a  cloud;  but  the  better 
education  for  the  great  majority  of  us  is  one  that  by 
the  faithful  study  in  all  their  relations  of  a  few  typical 
specimens  leads  us  to  a  deeper  and  broader  understand- 
ing of  the  whole  realm  of  nature,  including  man.  Only 
we  must  be  sure  that  so  far  as  we  do  go  in  any  direc- 
tion our  knowledge  is  accurate  and  thorough,  and  based 
upon  the  evidence  of  our  own  senses,  and  the  conclu- 
sions of  our  own  reason.  If  this  book  were  confined 
to  the  study  of  the  physical  properties  of  minerals 
merely,  as  their  form,  weight,  and  color,  and  to  a  con- 


176  THE   WORLD   OF  MATTER. 

sideration  of  those  changes  only  which  are  produced 
in  them  by  physical  forces,  such  as  motion  and  heat,  it 
might  have  been  called  a  "natural  philosophy"  or 
"physics;"  if  it  treated  only  of  the  composition  and 
decomposition  of  minerals,  and  of  those  more  in- 
timate changes  which  are  effected  when  different  ele- 
ments are  brought  into  chemical  contact,  it  would  have 
been  a  kind  of  chemistry;  while  if  it  had  considered 
mineral  specimens  merely  as  such,  describing  their  ap- 
pearance, structure,  and  uses,  teaching  how  to  recognize 
them  at  sight,  and  telling  where  they  may  be  found,  it 
would  have  been  essentially  a  little  work  on  mineralogy. 
As  it  includes,  however,  as  much  of  all  these  varieties 
of  knowledge  as  seems  necessary  to  a  clear  and  com- 
prehensive understanding  of  a  few  of  the  more  com- 
mon minerals,  and  to  show  how  the  others  should  be 
studied,  it  has  seemed  best  to  give  it  the  more  modest 
title  which  it  bears:  A  Guide  to  the  Study  of  Minerals. 

It  is  our  hope,  therefore,  not  to  give  our  readers  the 
unfounded  notion  that  they  have  "finished  mineralogy," 
but  to  show  them  how  they  may  now  profitably  begin 
that  important  study;  and  if  those  who  follow  us 
through  this  book  shall  find  themselves  better  able  to 
read  with  pleasure  and  understanding  the  standard 
works  on  physics,  chemistry,  and  mineralogy,  and  to 
perceive  how  these  are  all  related  to  one  another,  we 
shall  feel,  as  the  old  phrase  runs,  "that  our  labor  has 
not  been  in  vain !" 

The  proper  order  for  your  future  study  seems  to  me 
to  depend  upon  the  principle  that  the  simpler  or  more 


BY   WAY   OF   REVIEW.  177 

e/ementarv  should  come  before  the  more  complex ;  the 
i^wer  should  precede  the  higher.  In  any  doubtful 
case  you  may  determine  which  of  two  branches  of 
science  is  the  lower  and  which  the  higher  by  applying 
a  law  first  clearly  stated  by  President  Mark  Hopkins, 
of  Vvilliams  College.  He  calls  it  the  "law  of  the  con- 
ditioning and  the  conditioned."  It  is  very  simple,  and 
is  this: 

Whatever  is  a  necessary  condition  of  the  existence 
of  anything-  else,  is  as  a  rule  lower  than  that  of  which 
it  is  the  condition. 

For  example,  in  the  three  kingdoms  of  nature,  ani- 
mal, vegetable,  and  mineral,  the  mineral  kingdom  is  a 
necessary  condition  for  the  existence  of  the  vegetable 
kingdom,  and  the  vegetable  kingdom  is  a  necessary  con- 
dition for  the  existence  of  the  animal  kingdom.  There- 
fore, the  mineral  kingdom  is  the  lowest,  and  the  animal 
kingdom  is  the  highest. 

Using  this  principle,  now,  to  help  us  arrange  a  right 
course  of  scientific  study,  we  shall  find  that  the  student 
having  mastered  the  rudiments  of  language,  arithmetic, 
and  geography,  should  first  be  made  familiar — as  we 
have  been  by  our  simple  observations  and  experiments 
— with  the  more  common  elements  of  the  mineral 
world;  at  the  same  time  learning  the  laws  which  govern 
their  physical  and  chemical  changes.  Having  studied 
then,  physics,  chemistry,  and  mineralogy,  he  will  be 
led  to  observe  how  from  the  mineral  or  inorganic  world, 
life  first  springs  in  the  lower  and  higher  forms  of 
vegetable  growth,  and  he  will  naturally  make  a  study 


178  THE  WORLD  OF  MATTER. 

of  plants  with  the  aid  of  some  standard  botany.  The 
consideration  of  animal  life  will  follow,  including 
zoology,  anatomy,  and  physiology. 

A  good  review  of  the  last  four  branches  will  be  ob- 
tained by  reading  a  good  biology,  and  making  the  ob- 
servations and  experiments  therein  described. 

Geology  will  follow,  and  while  pursuing  it,  the 
student  will  find  to  his  delight  that  all  his  previous 
work  has  been  directly  preparatory  to  a  clear  under- 
standing of  the  structure  of  the  earth. 

Astronomy  may  well  come  next,  and  is  but  the  ex- 
tension to  other  worlds  of  the  same  methods  of  study 
that  have  given  a  knowledge  of  the  earth.  By  this 
time  the  student  will  have  laid  a  firm  foundation  on 
which  he  can  stand  when  he  approaches  the  study  of 
the  human  intellect,  and  the  supreme  questions  and 
problems  involved  in  moral  philosophy  and  natural 
theology. 

QUESTIONS  ON  CHAPTER   19. 

1.  Give  an   outline    or    synopsis    of   the    preceding 
chapters. 

2.  Explain    the    connection    between    the    several 
natural  sciences. 

3.  How  many  different  sciences  contribute  to  a  com- 
plete understanding  of  minerals? 

4.  What  is  Hopkins'   law    of  the  conditioning  and 
conditioned  ? 

5.  Give  an  illustration  of  its  working. 

6.  Give  the  natural  order  of  studying  the  sciences 
in  accordance  with  this  law. 


WHAT  IS  A  METAL?  179 


CHAPTER  XX.    , 

WHAT    IS    A    METAL? 

We  have  now  become  somewhat  familiar  with  eleven 
of  the  most  common  and  abundant  elements,  namely, 
oxygen,  hydrogen,  nitrogen,  chlorine,  carbon,  silicon, 
sodium,  potassium,  calcium,  aluminum,  and  iron;  and 
we  have  incidentally  become  acquainted  with  quite  a 
number  of  their  more  important  compounds. 

It  is  now  time  to  compare  these  elements  with  one 
another  for  the  purpose  of  arranging  them  if  possible 
in  groups  or  classes. 

To  clo  this  properly  we  must  group  together  ele- 
ments which  have  certain  properties  in  common,  and 
the  more  essential  and  important  the  properties  are 
which  we  select  as  a  basis  for  our  classification,  the 
better  our  work  will  be.  Every  mind,  whether  edu- 
cated or  not,  is  more  or  less  constantly  busy  in  classifying 
the  objects  with  which  it  becomes  acquainted.  Child- 
ren and  illiterate  persons  commonly  seize  upon  the 
most  obvious  peculiarities  or  characteristics  of  the  ob- 
jects they  perceive  as  a  means  of  grouping  them,  color 
and  size  being  perhaps  most  frequently  selected.  Thus 
many  birds  and  fishes  are  popularly  named  from  their 
colors,  as  black-birds,  and  black-fish,  blue-birds,  and  blue- 
fish,  yellow-birds,  white-fish,  and  the  like.  In  the  case 


i£o  THE  WORLD  OF  MATTED. 

of  minerals,  this  method  would  evidently  be  unwise,  for 
as  we  have  seen  the  same  mineral  often  appears  of 
many  different  colors.  We  might  better  use  the  "streak" 
as  a  basis  of  classification,  but  even  this  would  fail  us 
in  the  case  of  liquids  and  gases. 

It  might  seem  at  first  thought  that  an  excellent  plan 
would  be  to  group  together  in  one  class  the  gases,  in 
another  the  liquids,  and  in  another  the  solids;  but  when 
we  remember  that  very  many  substances  readily  pass 
from  one  of  these  states  into  another,  we  see  that  this 
would  be  unsatisfactory,  unless  we  also  indicated  the 
temperature. 

Probably  the  best  and  simplest  general  division  of 
minerals  is  that  which  separates  them  into  metals  and 
non-metals. 

While  it  might  puzzle  you  to  give  a  true  definition 
of  a  metal,  yet  of  the  eleven  elements  we  have  studied 
you  would  have  no  difficulty  in  recognizing  as  metallic 
iron,  sodium,  potassium,  calcium,  and  aluminum,  and 
the  other  six  as  non-metallic.  You  would  probably 
rest  this  decision  chiefly  upon  the  peculiar  lustre  of 
the  metals,  and  upon  their  fine  texture  or  grain. 

In  this  case  you  would  be  right,  and  these  character- 
istics are  generally  sufficient  to  enable  us  to  recognize 
pure  metals  at  sight,  but  in  the  case  of  compounds  of 
the  metals,  such  as  ores,  we  need  a  more  intimate 
knowledge  of  their  essential  properties. 

The  chemist's  conception  of  a  metal  is  determined 
rather  by  the  nature  of  the  compounds  it  helps  to  form 
than  by  its  lustre  and  grain. 


WHAT  IS   A   METAL?  181 

You  have  already  met  with  a  number  of  compounds 
called  acids ^  notably  hydrochloric,  nitric,  and  sulphuric 
acids,  and  you  have  noted  the  sharp  taste,  and  the  pow- 
erful corrosive  action  which  they  possess;  likewise 
their  effect  in  changing  the  color  of  blue  litmus  to  red. 

You  have  also  met  with  another  and  different  kind  of 
compounds,  called  alkalies,  potash  for  example,  whose, 
action  is  precisely  opposite  to  that  of  acids,  so  that  acids 
and  alkalies  are  said  to  neutralize  each  other. 

Now  these  alkalies  are  typical  examples  of  a  class  of 
substances  known  as  bases,  whose  properties  are  di- 
rectly opposite  to  the  properties  of  acids. 

Among  the  more  common  bases  are  caustic  soda. 
NaOH;  caustic  potash,  KOH,  and  lime,  CaO2H2. 

You  will  notice  that  all  of  these — and  the  same  is 
true  of  all  the  other  bases — are  formed  by  the  union  of 
a  metal  with  oxygen  and  hydrogen.  You  will  also 
observe  that  all  acids  contain  hydrogen,  but  no  metal. 

Let  us  now  try  the  effect  of  combining  an  acid  with 
a  base. 

Dissolve  ten  grains  of  caustic  soda  in  a  glass  of 
water.  Add  hydrochloric  acid  slowly,  testing  the  solu- 
tion from  time  to  time  by  dipping  into  it  a  piece  of  blue 
litmus-paper.  As  long  as  the  solution  causes  no  change 
in  the  color  of  the  paper,  you  may  know  that  it  re- 
mains alkaline;  the  instant  the  solution  changes  the 
blue  of  the  paper  to  red,  you  know  that  it  has  passed 
the  point  of  neutralization.  When  this  point  is  reached, 
pour  the  water  into  a  saucer  and  evaporate  to  complete 
dryness.  Taste  the  substance  remaining.  It  is  com- 


i8a  THE   WORLD   OF  MATTER. 

mon  salt  or  sodium  chloride.  Is  it  an  alkali?  Is  it  an 
acid  ?  Is  it  neutral  ? 

.Its  formation  may  be  represented  by  the  following 
equation : 

HCH-NaOH:=:NaCH-H2O. 

Notice  that  the  hydrogen  of  the  acid  has  changed 
places  with  the  metal  of  the  base,  and  that  the  result  is 
water  and  salt.  We  may  now  sum  up  the  results  of 
our  study  thus: 

An  acid  is  a  substance  containing  hydrogen,  which  it 
easily  exchanges  for  a  metal. 

A  base  is  a  substance  containing  a  metal  combined 
with  oxygen  and  hydrogen,  and  it  easily  exchanges  its 
metal  for  hydrogen  when  treated  with  an  acid. 

The  products  of  the  action  of  an  acid  on  a  base  are 
first  water,  and  then  a  neutral  substance  called  a  salt. 
Sodium  chloride,  potassium  chloride,  sodium  nitrate, 
potassium  nitrate,  and  sodium  sulphate  are  salts. 

Bases  being  composed  of  metals  with  hydrogen  and 
oxygen  are  commonly  called  hydroxides  of  their 
metals.  Thus  Caustic  soda  is  sodium  hydroxide. 

Every  metal  can  form  a  salt  with  every  acid.* 

It  was  once  thought  that  oxygen  was  a  necessary 
part  of  every  acid,  and  hence  it  obtained  its  name, 
which  means  acid-former.  And  although  we  have 
learned  that  there  are  exceptions  to  this — as  in  the  case 
of  hydrochloric  acid,  HC1 — it  is  still  believed  that  acid 
properties  are  generally  due  to  oxygen. 

*  While  this  statement  is  theoretically  true,  it  must  not  be  understood  that 
every  metal  has  been  actually  combined  with  every  acid  to  form  a  salt.  Many 
theoretical  salts  are  still  practically  unknown  to  the  chemist. 


WHAT  IS   A   METAL?  183 

It  will  now  be  clearer  to  you  why  it  is  reasonable  to 
divide  the  elements  into  two  classes,  metals  and  non- 
metals;  and  you  will  also,  at  least  partly,  understand  the 
division  of  compounds  into  acids,  bases,  and  salts. 

QUESTIONS    ON    CHAPTER    2O. 

1.  Into    what    two    classes    may   the   elements   be 
divided  ? 

2.  What  is  an  acid? 

3.  What  is  abase? 

4.  What  is  a  salt? 

5.  What  effect  has  an  acid  on  a  base? 

6.  What  are  hydroxides? 

7.  Derivation  of  the  name  oxygen? 


184  THE   WORLD   OF  MATTER. 


CHAPTER  XXI. 

FAMILIES    OF  ACID-FORMING    ELEMENTS. 

The  eleven  elements  which  we  have  thus  far  con- 
sidered constitute  at  least  ninety-nine  per  cent,  of  the 
whole  substance  of  the  earth.  Most  of  the  other  ele- 
ments are  of  comparatively  rare  occurrence. 

It  will  be  well,  however,  briefly  to  glance  at  the  more 
important  of  them.  In  the  preceding  chapter  we 
learned  to  divide  the  elements  into  metals  and  non- 
metals;  recognizing  the  metals  partly  by  their  peculiar 
lustre  and  grain,  and  partly  by  the  fact  that  they  are 
base-forming  elements  in  distinction  from  acid-forming 
elements.  We  might  also  have  observed  that  as  a 
rule  they  are  insoluble,  or  soluble  with  difficulty,  that 
they  are  opaque,  that  many  of  them  can  oe  beaten  into 
thin  leaves,  or  drawn  into  slender  wire;  and  that  most 
of  them  make  a  ringing  sound  when  dropped  on  any 
hard  substance. 

Proceeding  now  to  a  further  subdivision  of  the  ele- 
ments, we  notice  that  they  naturally  fall  into  families, 
according  to  their  chemical  properties,  the  members  of 
each  family  showing  striking  resemblances. 

Taking  first  the  acid-forming  elements,  by  far  the 
smaller  of  the  two  great  divisions,  as  most  of  the  ele- 
ments are  metallic,  we  have  the  following  families: 


FAMILIES  OF  ACID-FORMING  ELEMENTS.     185 

Chlorine  Family.  Sulphur  Family.  Nitrogen  Family.  Carbon  Family. 
Chlorine  Sulphur  Nitrogen  Carbon 

Bromine  Selenium  Phosphorus       Silicon 

Iodine  Tellurium  Arsenic 

Fluorine  Oxygen  Antimony 

It  will  not  be  necessary  to  go  into  details  in  dealing 
with  these  families.  You  have  already  studied  one  or 
more  typical  members  of  each  of  them  except  the  sul- 
phur family,  and  the  other  members  may  be  treated 

briefly. 

THE    CHLORINE    FAMILY. 

The  two  members  of  this  family  which  show  the 
most  marked  resemblance  to  chlorine  are  bromine  and 
iodine.  Fluorine  is  not  known  in  the  free  state.  Its 
compounds,  however,  resemble  the  compounds  of 
chlorine,  and  hence  the  element  is  generally  included  in 
this  family. 

Bromine,  at  ordinary  temperatures,  is  a  heavy  dark 
red  liquid,  which  is  easily  converted  into  vapor.  It  has 
an  extremely  disagreeable  odor,  as  is  implied  in  its 
name,  which  means  a  stench.  Its  properties  are,  in 
general,  like  those  of  chlorine,  with  which  it  is  found 
associated  in  nature  in  salt-beds,  and  usually  in  the  form 
of  sodium  bromiJe,  or  potassium  bromide.  It  acts 
violently  upon  animal  and  vegetable  substances,  at- 
tacking particularly  the  skin  and  the  membranes  lining 
the  passages  of  the  throat  and  lungs.  It  must  therefore 
be  handled  with  great  care.  Its  many  compounds  with 
other  elements  are  called  bromides. 

Iodine  occurs  in  nature  in  composition   with    sodium. 


i86  THE  WORLD  OF  MATTER. 

in  company  with  chlorine  and  bromine,  but  in  smaller 
quantities.  It  also  occurs  plentifully  in  sea-plants. 

In  some  parts  of  the  ocean  sea-weed  is  cultivated  for 
its  bromine.  At  ordinary  temperatures  iodine  is  a  gray- 
ish black,  crystallized  solid.  It  melts  easily  and  boils, 
forming  a  violet  vapor. 

To  see  this  vapor,  mix  about  a  grain  of  potassium 
iodide  with  twice  its  weight  of  manganese  dioxide.  Add 
a  little  sulphuric  acid  in  a  test-tube,  and  heat  gently. 
In  the  upper  part  of  the  tube  some  crystals  of  iodine 
will  be  deposited. 

When  a  solution  containing  free  iodine  is  treated  with 
a  little  starch-paste  the  solution  turns  blue.  Bromine 
and  chlorine  do  not  form  blue  compounds,  and  this  is 
one  means  of  distinguishing  iodine  from  them. 

Test  this  by  grinding  a  few  grains  of  starch  to  a 
paste  with  cold  water  in  a  saucer,  and  adding  a  cup  of 
boiling  water.  After  cooling  add  a  little  of  this  paste 
to  a  dilute  water-solution  of  iodine. 

Fluorine  occurs  in  nature  in  large  quantity,  and 
widely  distributed,  but  never  alone.  It  is  found  chiefly 
in  combination  with  calcium,  in  the  form  of  fluor-spar, 
or  calcium  fluoride  (specimen  No.  4),  and  in  combination 
with  sodium  and  aluminum,  as  cryolite  (specimen  No. 
8),  a  mineral  which  occurs  abundantly  in  Green- 
land. 

A  very  powerful  acid  gas  is  made  by  treating  fluor- 
spar with  sulphuric  acid.  It  is  known  as  hydrofluoric 
acid,  greatly  irritates  the  vocal  organs,  being  therefore 
dangerous  to  inhale,  and  has  the  property  of  dissolving 


FAMILIES  OF  ACID-FORMING  ELEMENTS.     187 

glass.     For  this  reason  it  must  be    kept   in    vessels  of 
rubber,  lead,  or  platinum. 

It  is  used  for  etching  on  glass,  particularly  for  making 
scales  on  thermometers  and  other  glass  instruments.  If 
you  would  observe  this  action  of  hydrofluoric,  acid  on 
glass,  put  five  or  six  grains  of  powdered  fluor-spar  into 
a  leaden  vessel  and  pour  over  it  enough  concentrated 
sulphuric  acid  to  make  a  thick  paste.  Cover  the  surface 
of  a  piece  of  glass  with  a  thin  layer  of  wax  or  paraffine, 
and  scratch  some  letters  through  this  down  to  the  glass. 
Put  the  glass,  waxed-side  down,  over  the  vessel  contain- 
ing the  fluor-spar,  and  let  it  stand  half  a  day.  On  re- 
moving the  glass  and  scraping  off  the  wax  the  letters 
will  be  found  etched  on  the  glass. 

SULPHUR    FAMILY. 

Sulphur  is  familiar  to  every  one  from  its  use  in  the 
manufacture  of  matches,  and  from  its  increasing  em- 
ployment as  a  disinfectant.  Sulphur  candles  are  now 
burned  in  most  well-regulated  households,  after  every  case 
of  measles,  scarlet  fever,  or  other  contagious  or  infec- 
tious disease.  Sulphur  occurs  in  nature  both  free  and 
in  combination  with  many  metals.  It  is  found  free  in 
certain  volcanic  countries,  especially  Sicily  and  Iceland, 
in  transparent,  yellow,  rhombic,  octahedral  crystals, 
Fig.  28. 

The  compounds  of  sulphur  with  metals  are  called 
sulphides ,  and  they  constitute  the  ores  from  which  the 
metals  are  usually  obtained.  Thus  lead  sulphide,  or 
galena  (specimen  No.  30),  zinc  sulphide  or  blende,  and 


1 88  THE   WORLD   OF  MATTER. 

copper  sulphide  are  the  substances  from  which  lead, 
zinc,  and  copper  are  generally  procured.  Sulphur  also 
occurs  naturally  combined  with 
metals  and  oxygen,  and  such 
compounds  are  called  sul- 
phates. Of  these  calcium  sul- 
phate or  gypsum  (specimen 
No.  2),  barium  sulphate  or 
heavy  spar,  and  sodium  sul- 
phate or  Glauber's  salt  occur 
in  the  largest  quantity.  Pure 
'  28.  sulphur,  like  pure  water,  is  ob- 

tained by  distillation.  If  the  vapor  of  sulphur  is  quickly 
cooled  below  its  melting  point  it  solidifies,  or  "freezes," 
in  the  form  of  a  fine  crystalline  powder,  or  "snow," 
called  "flowers  of  sulphur;"  in  this  particular  also  bear- 
ing a  marked  resemblance  to  water. 

When  sulphur  is  gently  heated  it  melts,  and  may  be 
cast  into  sticks,  when  it  is  known  as  brimstone  or  roll 
sulphur.  Sulphur  burns  with  a  bluish  flame,  combin- 
ing with  oxygen  to  form  sulphur  dioxide  (often  called 
sulphurous  acid),  which  is  given  off  as  a  gas,  having 
that  peculiar  suffocating  odor  which  is  perceived  when 
a  common  match  is  lighted. 

.  Sulphur  is  one  of  the  most  interesting  and  important 
elements,  and  can  be  obtained  at  trifling  cost.  It  will 
well  repay  you  to  make  a  careful  study  of  it.  Allow 
melted  sulphur  to  cool  slowly,  and  observe  the  long, 
transparent,  needle-like,  prismatic  crystals  which  are 
formed,  so  different  from  the  natural  crystals  repre- 
sented in  Fig.  2$. 


FAMILIES  OF  ACID-FORMING  ELEMENTS.    189 

Expose  these  transparent  crystals  to  the  air  for  a  few 
days,  and  observe  the  curious  changes  that  take  place 
in  them. 

Pour  melted  sulphur  heated  to  230  degrees  into  cold 
water,  and  observe  the  soft,  india-rubber-like  mass  that 
is  produced.  Remove  this  from  the  water  and  expose 
it  for  a  few  hours  to  the  air,  What  change  do  you 
notice? 

Sulphur  combines  directly  with  chlorine,  carbon,  and 
most  other  elements,  and  many  metals  burn  in  sulphur 
vapor  as  in  oxygen,  uniting  with  it  to  form  sulphides. 

Sulphuric  acid,  or  hydrogen  sulphate,  H2SO4,  is  the 
most  important  and  useful  acid,  as  by  its  means  nearly 
all  other  acids  are  prepared,  and  also  because  it  is  used 
in  the  arts  and  manufactures  for  a  great  variety  of 
purposes. 

It  has  been  said  that  the  commercial  prosperity  of  a 
country  may  be  judged  with  great  accuracy  by  know- 
ing the  amount  of  sulphuric  acid  which  it  consumes. 
Among  its  many  uses  are  the  making  of  "soda,"  or 
sodium  carbonate,  which  is  necessary  for  the  manufac- 
ture of  soaps  and  glass;  the  production  of  phosphorus 
and  of  artificial  fertilizers;  and  the  refining  of  petro- 
leum. More  than  a  million  tons  of  sulphuric  acid  are 
manufactured  each  year  in  the  United  States  and  Great 
Britain.  It  is  the  most  important  manufactured  chemi- 
cal substance. 

Selenium  and  tellurium  are  so  rare  elements,  and 
so  closely  resemble  sulphur  in  their  chemical  character- 
istics, that  we  pass  them  by.  There  is  no  great  advan- 


ipd  THE   WORLD   OF  MATTER. 

tage  in  describing   to  you  substances    that   you   cannot 
bring  under  your  own  observation. 

Oxygen  we  have  already  studied  together  as  fully  as 
is  necessary  for  our  present  purpose.  It  is  the  most 
acid  element,  and  may  quite  properly  be  classed  by 
itself  instead  of  being  included  in  any  "family." 

THE    NITROGEN    FAMILY. 

Having  found  nitrogen  in  the  air,  and  studied  its  prop- 
erties, we  will  glance  at  its  allied  elements,  phosphorus, 
arsenic,  and  antimony.  Phosphorus  is  not  found 
naturally  in  its  free  state,  but  combined  with  oxygen 
and  calcium — in  the  form  of  phosphates — in  the  seeds 
of  plants,  the  bodies,  and  especially  the  bones,  of  ani- 
mals, and  in  the  minerals,  apatite  (specimen  No.  5) 
and  phosphorite.  When  bones  are  burned  a  white 
solid  mass  remains,  which  is  called  calcium  phosphate, 
or  phosphate  of  lime.  Animals  obtain  their  phosphates 
from  plants,  which  in  their  turn  draw  their  supply  from 
the  soil.  Finally  soils  derive  their  phosphates  from  the 
gradual  grinding  up,  or  disintegration,  of  the  oldest 
granite  rocks  which  contain  this  element  dispersed  in 
small  quantities. 

Phosphorus  is  separated  from  bone-ash  by  mixing 
the  ash  with  sulphuric  acid,  adding  charcoal  to  the  mix- 
ture, and  heating  it. 

Phosphorus  distils  over,  and  is  condensed  and  cast  in 
sticks  under  water.  It  has  to  be  kept  under  cold  water 
until  used,  for  in  the  air  it  rapidly  combines  with  oxygen, 
and  takes  fire  with  very  slight  friction.  It  is  a  slightly 


FAMILIES  OF  ACID-FORMING  ELEMENTS.     191 

yellow,  semi-transparent  solid,  resembling  wax.  In 
the  air  it  gives  off  white  fumes,  and  emits  a  pale  phos- 
phorescent light,  visible  in  the  dark.  From  this  prop- 
erty it  derives  its  name,  phosphorus  signifying  in 
Greek  a  bringer  of  light.  Great  care  must  be  used  in 
handling  this  substance,  and  it  should  always  be  cut 
under  water.  Phosphorus  not  only  combines  thus 
readily  with  oxygen,  but  also  with  other  elements,  such 
as  chlorine,  bromine,  and  iodine.  Bring  together  in  a 
porcelain  crucible,  or  a  saucer,  a  little  phosphorus  and 
iodine.  Direct  combustion  takes  place,  accompanied  by 
light  and  heat. 

If  yellow  phosphorus  be  left  in  the  light,  or  heated 
to  about  240  degrees  for  some  hours  without  access  of 
air,  it  undergoes  a  very  remarkable  change,  and  is  con- 
verted into  a  dark  and  opaque  substance,  which  differs 
as  much  from  ordinary  phosphorus  as  graphite  differs 
from  the  diamond.  Ordinary  phosphorus,  as  we  have 
seen,  combines  actively  with  oxygen;  red  phosphdrus 
is  inactive;  ordinary  phosphorus  is  very  poisonous,  its 
vapor  even,  when  inhaled,  producing  a  disease  of  the 
bones;  red  phosphorus  is  not  poisonous;  ordinary  phos- 
phorus is  soluble  in  carbon  disulphide;  red  phosphorus 
is  not. 

Oiclinary  friction-matches  are  tipped  with  a  mixture 
of  phosphorus,  glue,  and  potassium  chlorate,  usually 
assisted  by  a  little  sulphur. 

Arsenic  occurs  naturally  combined  with  iron,  copper, 
nickel,  and  other  metals,  and  also  as  an  oxide.  Pure 
arsenic  has  a  metallic  lustre.  When  heated  sufficiently 


102  THE   WORLD   OF   MATTER. 

in  the  air  it  burns  with  a  bluish  flame,  yielding  poison- 
ous fumes  that  have  the  odor  of  garlic  or  onions. 
Arsenic  in  its  pure  state  is  not  poisonous,  but  becomes 
so  when  combined  with  oxygen. 

When  arsenic  oxide  is  added  to  a  mixture  from  which 
hydrogen  is  being  evolved  a  compound  of  arsenic  and 
hydrogen  is  formed.  It  is  known  as  arsine,  and  is 
represented  by  the  formula,  AsH3.  This  arsine,  which 
is  a  very  poisonous,  colorless  gas,  is  important  as  a 
means  of  detecting  the  presence  of  arsenic.  When 
heated,  it  separates  readily  into  arsenic  and  hydrogen, 
and  if  a  cold  object,  as  a  piece  of  porcelain,  is  brought 
into  the  flame  of  burning  arsine,  the  arsenic  is  deposited 
in  the  form  of  a  dark  spot.  Arsine  and  other  com- 
pounds of  arsenic  are  so  fatally  poisonous  that  we 
advise  you  to  make  no  experiments  with  them. 

Antimony  is  a  silver- white,  metallic-looking  substance. 
It  occurs  most  frequently  in  combination  with  sulphur. 

Boron  is  sometimes  classed  in  the  nitrogen  family,  to 
the  members  of  which  it  bears  many  resemblances, 
though  it  has  peculiarities  which  distinguish  it  from 
them.  It  occurs  in  nature  most  commonly  in  the  form 
of  borax,  the  salt  of  sodium.  It  can  be  obtained, 
though  not  easily,  in  the  form  of  crystals  which  are 
nearly  as  hard  as  diamonds. 

Borax  is  found  in  the  salty  incrustation  on  the  shores 
of  certain  lakes  in  Persia  and  Thibet,  and  also  in 
Nevada  and  California.  It  is  also  prepared  artificially. 
It  is  soluble  in  water,  yielding  a  clear  solution  with  a 
sweetish  taste.  It  is  of  great  service  in  blow-pipe  ex- 


FAMILIES  OF  ACID-FORMING  ELEMENTS.     193 

periments,  because  it  unites  with  the  various  metallic 
oxides  to  form  colored  glasses.  It  is  also  used  in  the 
manufacture  of  enamels  and  glazes,  and  in  the  formation 
of  "paste"  or  artificial  gems.  Its  domestic  uses  for 
cleansing  and  for  rendering  "hard"  water  "soft"  are 
well  known. 

Carbon  and  silicon,  the  two  elements  composing  the 
carbon  family,  have  been  considered  in  previous  chapters. 

QUESTIONS  ON  CHAPTER    21. 

1.  Name  four,  groups  or  "families"  of  acid-forming 
elements. 

2.  Describe  the  properties  and  uses  of  bromine,  iodine, 
and  fluorine. 

3.  What  is  the  effect  of  hydrofluoric  acid  upon  glass? 

4.  Describe    sulphur.     In     what     respects    does    it 
resemble  water? 

5.  Uses   of   sulphuric   acid?     What  is   its  chemical 
formula? 

6.  Describe  the   properties  and  uses  of  phosohorus. 
What  precaution  is  necessary  in  handling  it? 

7.  What  is  "red  phosphorus?" 
.    8.     Describe  arsenic. 

9.  What  is  arsine? 

10.  Describe  antimony. 

IT.  Describe  boron. 

12.  Composition,  properties,  and  uses  of  borax? 


194  ?Htf   WORLD   OF   MATTER. 


CHAPTER  XXII. 

FAMILIES    OF    METALS. 

The  metals  or  base-forming  elements— that  is  ele- 
ments whose  compounds  with  oxygen  and  hydrogen 
neutralize  acids  and  form  salts — may  be  conveniently 
grouped  as  follows:  , 

1.  The  potassium  family,   the  principal  members  of 
which  are  potassium  and  sodium. 

2.  The  calcium  family,  notably  calcium,  barium,  and 
strontium. 

3.  The  magnesium    family:   magnesium,  zinc,  and 
cadmium. 

4.  The  silver  family:  silver,  copper,  and  mercury. 

5.  The  aluminium  family,  of   which   aluminium  is 
the  only  well-known  member. 

6.  The  iron  family:  iron,  cobalt,  and  nickel. 

7.  The  manganese  family,  of  which  manganese  is  the 
only  representative. 

8.  The  chromium   family,    represented    chiefly    by 
chromium. 

9.  The  bismuth  family,    represented    only   by  bis- 
muth. 

TO.     The  lead  family:  notably  lead  and  tin. 
ii.     The  palladium    family,  consisting  of   three   rare 
elements. 


FAMILIES  OF  METALS.  195 

12.  The  platinum  family,  the  principal  members  of 
which  are  platinum  and  gold. 

It  has  been  before  observed  there  are  many  more 
metallic  than  non-metallic  elements.  It  would  not  be 
wise  to  try  to  describe  them  all  in  this  book;  indeed,  a 
thorough  acquaintance  with  all  the  elements  and  their 
compounds  can  hardly  be  acquired  in  a  life-time  of 
patient  study.  Fortunately,  however,  the  great  bulk  of 
the  minerals  of  the  world  is  composed  of  only  a  dozen 
different  elements,  and  only  a  few  different  compounds 
of  these;  and  the  methods  of  study  which  we  have  fol. 
lowed  in  the  case  of  these  commonest  substances  are 
equally  satisfactory  in  the  case  of  all  the  rest. 

Having  shown  you,  therefore,  how  to  study  the 
properties  of  these  most  important  elements,  we  may 
safely  leave  you  to  apply  similar  methods  of  observation 
to  the  others.  Those  that  you  will  especially  need  to 
examine  are  magnesium,  zinc,  copper,  mercury,  lead, 
tin,  silver,  platinum,  and  gold.  The  art  of  extract- 
ing these  metals  from  their  ores  is  known  as  metallurgy. 

You  will  find  the  following  classification  of  metallic 
compounds  convenient: 

1.  Compounds  with  chlorine,  bromine,  and  iodine; 
or  the  chlorides,  bromides,  and  iodides. 

2.  Compounds  with  oxygen,  and  oxygen  and  hydro- 
gen ;  or  the  oxides  and  hydroxides. 

3.  Compounds  with  sulphur  or  the  sulphides. 

\.  Compounds  with  nitric  and  nitrous  acids;  or  the 
nitrates  and  nitrites. 

5.  Compounds  with  the  acids  of  chlorine;  or  the 
chlorates,  chlorites,  etc. 


196  '  THE  WORLD   OF  MATTER. 

6.  Compounds  with  sulphuric  and  sulphurous  acids; 
or  the  sulphates  and  sulphites. 

7.  Compounds  with  carbonic  acid ;  or  the  carbonates. 

8.  Compounds  with  phosphoric  acid ;    or  the  phos-* 
p  hates. 

9.  Compounds  with  silicic  acid;  or  the  silicates. 
10.     Compounds  with  boric  acid;  or  the  borates. 

You  will  observe  in  the  foregoing  list  that  the  names  of 
some  acids  end  in  ic  and  the  names  of  others,  containing 
the  same  elements,  in  ous.  The  termination  ous  is  used 
to  indicate  that  less  oxygen  is  present  than  in  the  corre- 
sponding acid  whose  name  ends  in  ic.  Thus  sulphurous 
acid  consists  of  the  same  elements  as  sulphuric  acid,  but 
contains  less  oxygen,  as  is  shown  by  their  chemical 
formulas,  thus: 

Sulphuric  acid  =  H2SO4. 

Sulphurous  acid  =  H2SO3. 

Notice  also  that  the  names  of  compounds  of  acids 
whose  names  end  in  ic,  end  in  ate;  while  the  names  of 
compounds  of  acids  whose  names  end  in  ous,  end  in  ite; 
thus  the  salts  derived  from  nitric  acid  are  called 
nitrates,  while  the  salts  derived  from  nitrous  acid  are 
called  nitrites. 

EXERCISES    FOR    CHAPTER   22. 

1.  Observe  a  piece  of  magnesium  wire.    (Specimen 
No.  31.)     Note  its  color  and  hardness.     Test  its  malle- 
ability and  flexibility.     Is  it  elastic?  Set  fire  to  the  wire 
and  observe  its  splendid  combustion. 

2.  Study  the  physical  properties  of  copper,  zinc,  lead, 


FAMILIES   OF  METALS.  197 

and  tin,  procuring  if  possible  not  only  a  specimen  of 
the  sheet  metal,  but  also  rods  as  large  as  a  lead-pencil. 
Study  also  a  piece  of  solder,  which  is  a  mixture  of  tin 
and  lead;  a  piece  of  pewter  which  is  also  lead  and  tin, 
but  containing  a  much  larger  proportion  of  tin;  a  piece 
of  brass,  which  is  composed  of  about  six  parts  of  copper 
and  four  parts  of  zinc;  and  a  bit  of  bronze  which  con- 
tains ninety-five  parts  of  copper,  four  of  tin,  and  one  of 
zinc,  varying  to  seventy  parts  of  copper  and  eight  of  tin. 

Compare  the  color,  specific  gravity,  and  hardness  of 
copper,  zinc,  and  tin. 

Which  bends  most  easily? 

Which  "cries"  or  creaks  when  bent? 

Write  out  the  uses  of  each. 

Are  "tin"  pans  and  pails  made  wholly  of  tin? 

Test  the  fusibility  of  these  metals. 

3.  Observe  the  properties  of  mercury. 
What  is  its  popular  name? 

Try  to  freeze  it.    (It  becomes  solid  at — 40  degrees  F.) 
How  does  its  weight  compare   with  that   of  water? 

Ascertain   by    reading    or   inquiry  from  what  ore  it  is 

produced.     Make  a  list  of  its  uses. 

4.  Examine  a  piece  of  silver.     Compare  it  with  pure 
tin.   Testitwithacidsand  withfumesof  sulphur.  Itsuses? 

5.  Study  platinum  and  gold.     Note  their  resemblan- 
ces and  differences.      Which  is  the  more  easily  fusible? 

Test  the  effect  of  various  acids  upon  gold  and  plati- 
num. Test  the  effect  of  the  fumes  of  sulphur  upon 
them.  Consider  their  malleability,  and  examine  a  piece  of 
gold-leaf.  What  are  the  chief  uses  of  gold  and  platinum  ? 


198  THE   WORLD   OF  MATTER. 


CHAPTER  XXIII. 

HOW    TO    DETERMINE     MINE*RALS. 

When  you  find  a  new  mineral  one  of  the  first  ques- 
tions that  occurs  to  you  is,  What  is  it?  The  process  of 
finding  the  name  of  a  mineral  from  a  study  of  its  proper- 
ties is  called  "determining"  the  mineral,  and  the  vari- 
ous methods  of  accomplishing  this  determination  con- 
stitute a  science  by  themselves,  a  science  known  as 
determinative  mineralogy.  The  simplest  method  of 
determining  minerals,  and  a  method  that  is  sufficient  for 
most  of  the  common  varieties,  depends  upon  the  study 
of  their  physical  properties.  As  I  have  repeatedly  said, 
there  is  no  use  at  all  in  trying  to  study  mineralogy  un- 
less you  have  the  minerals  in  your  hand,  and  unless  you 
make  the  observations  upon  them  yourself,  and  with 
the  least  possible  help.  For  this  reason  the  collec- 
tion accompanying  this  book  has  been  prepared.  You 
have  already  found  it  useful  as  a  means  of  illustrating 
the  previous  chapters.  It  remains  to  make  use  of  it  in 
showing  you  the  simpler  methods  of  determining  the 
minerals  you  may  hereafter  obtain.  For  this  purpose 
the  specimens  are  numbered  but  not  named.  There  is 
a  key  to  the  collection  at  the  end  of  this  book,  but  you 
are  not  to  refer  to  it  until  you  have  done  your  best  to 
determine  the  names  of  the  specimens  by  the  method 


HOW   TO   DETERMINE   MINERALS.  199 

now  to  be  described.  After  you  Have  decided  on  these 
names  as  well  as  you  can,  you  may  turn  to  the  key  to 
satisfy  yourself  as  to  the  correctness  of  your  determina- 
tions. 

We  will  first  try  only  a  dozen  of  the  most  easily  re- 
cognized specimens.  Select  from  the  collection  num. 
bers  i,  2,  3,  5,  6,  7,  1 1,  29,  26,  28,  30,  and  32. 

Examine  these  specimens,  noting  their  hardness, 
color,  streak,  etc.,  and  write  a  description  of  each.  Then 
by  comparing  your  observations  with  the  following 
brief  descriptions,  determine  the  name  of  each  speci- 
men. Of  course,  the  descriptions  here  given  will  not 
follow  the  numbered  order  of  the  specimens. 

HINTS. 

The  only  tools  needed  are  the  streak  and  scratch- 
plate  (furnished  with  the  collection),  and  a  pocket- 
knife. 

In  using  the  glass  plate  to  test  hardness  or  streak,  do 
not  scratch  the  plate  all  over  with  your  specimen.  A 
scratch  or  streak-line  as  long  as  this is  sufficient. 

Generally  the  color  of  the  streak  will  be  seen  better 
if  the  streak-plate  is  put  upon  a  piece  of  white  paper. 

Whenever  you  have  made  out  a  mineral,  write  the 
name  on  a  small  label  and  place  it  in  the  compartment 
with  the  specimen. 

Sometimes  the  mineral  to  be  determined  forms  only 
a  part  of  the  specimen.  A  portion  of  the  rock  in  which 
the  mineral  occurs  may  be  present,  or  some  other  asso- 
ciated mineral.  In  this  case  try  to  find  which  is  the 


200  THE   WORLD   OF   MATTER. 

essential  mineral,  and  see  whether  you  cannot  deter- 
mine also  the  others  that  accompany  it. 

Hardness. — Find  out  how  many  of  the  twelve  speci- 
mens you  can  scratch  with  your  finger-nail  and  put  these 
aside;  then  find  the  softer  and  harder  ones  among  these; 
see  what  minerals  described  below  have  hardness  i  and 
2,  and  from  the  description  try  to  determine  which 
specimen  is -talc,  which  is  kaolin,  graphite,  gypsum, 
etc.  Label  all  those  you  have  determined;  the  other 
specimens  try  with  your  knife;  do  not  disfigure  the 
whole  specimen  with  scratches;  a  little  scratch  in  some 
corner  will  tell  the  story,  and  the  specimen  will  be  as 
good  as  before.  Put  aside  all  those  you  can  scratch 
with  your  knife,  separating  those  that  you  can  scratch 
easily  from  those  that  require  force.  The  hardest  of 
these  will  scratch  the  glass  plate  (the  smooth  side  of 
this  is  to  be  used  for  receiving  the  scratches.)  In  this 
manner  you  will  find  the  minerals  that  have  hard- 
ness 3  to  6.  The  specimens  that  are  still  left  will 
scratch  the  glass  easily;  they  will  have  hardness  7  or  8. 

Lustre. — Examine  a  porcelain  dish,  a  mother-of-pearl 
button,  a  piece  of  white  wax,  white  satin  or  silk,  and  a 
silver  dollar:  All  these  are  white,  but  each  has  a  differ- 
ent lustre;  each  reflects  the  light  differently.  The 
lustre  of  minerals  often  resembles  that  of  glass,  or  wax, 
or  silk,  or  pearl;  these  minerals  are  said  to  have  a 
glassy  (vitreous),  waxy,  silky,  or  pearly  lustre. 

In  examining  the  minerals  for  their  lustre,  notice  first 
whether  the  lustre  is  metallic  or  non-metallic.  If 
the  specimen  does  not  shine  like  silver,  or  gold,  or 


HOW   TO   DETERMINE   MINERALS.  201 

brass,  or  copper,  or  steel,  or  any  other  metal,  the  lustre 
is  non-metallic;  you  will  judge  next  whether  the  lustre 
of  your  specimen  resembles  that  of  glass,  or  pearl,  or 
resin,  etc.  Minerals  that  have  no  lustre,  such  as  chalk  and 
clay,  are  called  dull.  In  some  minerals  the  lustre  looks 
somewhat  metallic,  but  not  clearly  so;  for  these  the 
term  sub-metallic  is  used. 

Transparency. — Some  minerals  are  as  clear  as  glass; 
they  are  transparent;  some  let  the  light  through  dimly, 
like  thin  China  ware;  they  are  translucent;  some 
do  not  let  any  light  through;  they  are  opaque.  Semi- 
transparent  means  half-transparent,  not  quite  clear  and 
not  very  dim;  the  streak-plate  is  a  good  example.  In 
some  minerals  a  faint  light  passes  only  through  the 
edges;  these  are  called  sub-  or  semi-translucent. 

STREAK. 

The  streak  or  powder  of  the  specimen  is  of  more  im- 
portance for  its  determination  than  the  color;  it  shows 
the  essential  color  of  the  mineral.  Most  of  the  minerals 
that  are  white  or  colorless  when  pure,  have  a  white 
streak  even  when  they  are  colored.  Take  some  clear 
glass  and  some  colored  glasses  and  grind  each  to  a  fine 
powder;  the  powder  will,  in  all  cases,  be  white  (with 
probably  a  faint  tint  of  color  in  some  instances),  because 
the  amount  of  coloring  matter  used  is  very  small.  To 
test  the  streak,  rub  one  of  the  edges  or  corners  of  the 
specimen  against  the  ground  side  of  the  streak-plate, 
causing  it  to  trace  a  small  line-  on  the  latter,  and  notice 
the  color.  The  minerals  of  the  hardness  of  7  and  8 


202  THE   WORLD   OF   MATTER. 

will  not  leave  any  trace  of  their  powder  on  the  glass 
because  they  scratch  it,  but  as  they  have,  almost  with- 
out exception,  a  white  or  grayish  streak,  it  is  not  neces- 
sary to  test  them.  Their  essential  color  may  be  found, 
however,  by  breaking  off  a  small  chip  and  grinding  it  to 
a  fine  powder. 

TASTE    AND    ODOR. 

A  few  mineral  salts  can  be  distinguished  by  their 
taste;  some  minerals  have  a  peculiar  odor;  in  kaolin, 
and  all  rocks  containing  clay,  the  clayey  or  argil- 
laceous odor  is  readily  noticed  after  breathing  upon 
them;  in  others  the  odor  is  brought  out  by  rubbing  the 
specimen  against  another  stone  or  by  breaking  it  with 
a  hammer. 

DESCRIPTION    OF    THE    TWELVE    MINERALS. 

I.'  Calcite  (calcspar). — Hardness,  3;  streak,  white; 
lustre,  vitreous;  color,  generally  white  or  light  colored, 
but  also  of  darker  colors ;  transparent  to  opaque.  The 
colorless,  transparent  variety  is  called  Iceland  spar. 
Marble  is  a  crystalline  variety  with  a  sugary  fracture. 
Limestone  is  a  common,  compact  variety. 

2.  Talc. — Hardness,  i ;  streak,  white;  lustre,  pearly; 
color,  greenish  to  white;  translucent;  smooth,  slippery, 
soapy  to  the  touch.     Commonly  called  soapstone,  also 
steatite  and  French  chalk.    Foliated  talc  can  be  separated 
with  a  knife  into  thin  scales,   somewhat  like  mica,  but 
mica  is  elastic,  talc  is  not. 

3.  Gypsum. — Hardness,    2;    streak,    white;    lustre, 


HOW   TO   DETERMINE   MINERALS.  203 

pearly,  glassy,  silky  or  dull;  color,  white,  'gray,  pink, 
brownish,  etc.  The  colorless,  transparent  variety  is  called 
selenite;  the  fibrous  variety,  satin  spar;  the  white  fine 
grained  variety,  alabaster.  Foliated  gypsum  resem- 
bles talc  and  mica,  but  it  is  not  greasy  to  the  touch  like 
talc,  and  it  is  not  split  as  easily  as  mica,  and  is  not  elastic. 

4.  Mica  (tnuscovite) — Hardness,    2;    streak,  white; 
lustre,  pearly,  somewhat  metallic;  color,  white  to  gray 
and  brownish.      Can   be  easily   split  into   thin   elastic 
leaves;  used  in  stoves.     Often  wrongly  called  isinglass. 
Isinglass  is  a  kind  of  glue,  made   from   the   air-bladder 
of  the  sturgeon,  and  used  for  making  jelly. 

5.  Fluorite    (fluor   spar}. — Hardness,    4;      streak, 
white;  lustre,  vitreous;  colorless  or  of  various  beautiful 
tints;  more  or  less  transparent.     The  specimen   in  this 
collection  resembles  calcite  and  quartz,  but  it  is   easily 
distinguished  by  its  hardness;  it  will  scratch  calcite  and 
will  be  scratched  by  quartz. 

6.  Quartz. — Hardness,  7;  streak,  white;  lustre,  vit 
reous;    color,    colorless    (rock     crystal);      also    white 
(milky  quartz;)    pink  (rose   quartz);    brown   or   nearly 
black     (smoky    quartz);      violet    (amethyst);    yellow 
(false  topaz).     These   and   some  others    are  the   glassy 
varieties  of  quartz;    all  these  are  transparent  to  translu- 
cent.     Nearly   all  the   light-colored  pebbles  found   on 
river  banks  or  lake  shores  are  quartz;  sand  is  usually 
composed  of  quartz  grains. 

7.  Orthoclase    (feldspar}. — Hardness,     6;      streak, 
white;  lustre,  vitreous.     Compare   this  specimen   with 
calcite.      Although  the  lustre  in  both  may  be  called 


204  THE   WORLD   OF  MATTER. 

glassy  (vitreous)  there  is  some  difference.  In  calcite 
the  lustre  is  easily  seen  in  all  directions.  In  orthoclase 
the  lustre  inclines  somewhat  to  the  silky,  and  you  have 
often  to  turn  the  specimen  around  in  your  fingers  and 
look  at  it  in  this  way  and  that  before  you  see  the  lustre 
plainly ;  examine  until  every  part  has  shown  its  lustre 
to  you.  Color,  white,  yellow,  gray,  pink,  and  other 
light  tints;  translucent,  at  least  at  the  edges,  sometimes 
transparent. 

8.  Apatite. — Hardness,  5;  streak,  white;  lustre,  vit- 
reous; color,  generally  green,   sometimes   brown,  yel- 
lowish or  white;   generally  opaque,  often  translucent 
at  the  edges. 

9.  Halite  (rock  salt]. — Hardness,  2 ;   streak,    white ; 
lustre,  vitreous;  color,  white,  gray,  red,  rarely  blue  or 
violet.     Taste,  salty. 

10.  Galenite  (lead  ore]. — Hardness,  2\\  streak,  lead- 
gray;    lustre,  metallic;    color,  gray.     Often  contains  a 
little  silver. 

11.  Hematite  {iron  ore)   (variety ,  specular  iron). — 
Hardness,  $J;  streak,  red;  (rub  on  the  streak-plate  and 
blow  away  the  shiny  scales  to  see  the  streak) ;  lustre  (of 
this  variety),    metallic;   color,   gray.     There  are  other 
varieties  of  hematite  iron  ore  of  different  lustre  and 
color,  but  the  red  streak  is  common  to  all. 

12.  Iron  pyrites  (JooPs  gold}. — Hardness,  6;  streak, 
dark  greenish   or   gray;    lustre,  metallic;   color,  brass- 
yellow;  sometimes  contains  gold.      To    distinguish  it 
from  gold,  hammer  it;  gold  flattens;  pyrites  crumbles 
into  a  dark,  greenish  powder. 


FLAME,  HEAT  AND  ACID  TESTS.         205 


CHAPTER    XXIV. 

FLAME    TESTS,    HEAT    TESTS,    AND    ACID    TESTS. 

The  properties  by  which  you  determined  the  names 
of  the  twelve  specimens  described  in  the  preceding 
chapter  are  those  which  enable  one  to  distinguish  a 
mineral  by  looking  at  it,  and  testing  it  by  means  of  a 
pocket-knife  and  a  streak. plate.  This  is  the  simplest 
method  of  determination,  and  the  student  should  try  to 
determine  by  it  as  many  specimens  as  possible.  But 
in  order  to  be  certain  that  the  determinations  are  cor- 
rect, and  also  that  he  may  learn  the  composition  of 
minerals,  he  must  learn  to  apply  other  tests  with  heat 
and  with  acids.  These  are  also  called  dry  and  wet 
tests. 

APPARATUS    NEEDED. 

•  For  these  tests  you  will  need  an  alcohol  lamp,  or  a 
Bunsen  gas-burner,  a  forceps — preferably  with  platinum 
points — small  open  and  closed  tubes  of  hard  glass,  and 
a  few  test-tubes. 

It  will  also  be  convenient,  though  not  necessary,  to 
have  a  small  agate  mortar  and  pestle;  a  few  small  por- 
celain dishes,  such  as  are  in  dolls'  "china  sets,"  and  a 
magnifying-glass. 


206  THE  WORLD   OF  MATTER. 

HINTS, 

Make  all  the  tests  yourself,  getting  from  a  friend  or 
teacher  any  further  suggestions  you  may  need  about 
the  handling  of  the  apparatus  or  the  acids. 

Small  fragments  chipped  from  each  specimen  will 
be  sufficient  for  all  the  tests. 

Be  careful  with  the  acids;  they  stain  and  burn. 

Be  neat  and  orderly.  A  noted  mineralogist  makes 
his  determinations  on  a  parlor  table,  and  makes  so  little 
dust  that  a  stroke  of  the  handkerchief  removes  all  traces 
of  his  work. 

Keep  your  apparatus  in  a  suitable  box. 

Clean  and  dry  all  apparatus  after  use. 

In  chapter  XV,  on  salt,  we  have  already  given  prac- 
tical directions  for  testing  the  colors  of  flames,  and  these 
need  not  be  repeated.  Before  studying  any  new  min- 
erals, however,  it  will  be  best  for  you  to  repeat  the  test 
there  described  for  showing  the  yellow  sodium  flame, 
and  also  to  make  the  following  simple  experiments  with 
the  specimens  treated  in  the  preceding  chapter. 

i.  Break  off  a  little  chip  of  calcite,  and  giving  it  a 
few  taps  with  a  hammer,  notice  how  it  breaks  into  little 
crystals,  some  of  them  quite  perfect.  Take  one  of  the 
larger  crystals  and  hold  it  in  the  flame.  Probably  it  will 
not  show  any  distinct  color,  but  will  fly  to  pieces  or 
"decrepitate." 

The  metal  calcium,  which  is  in  calcite,  gives  the 
flame  an  orange  color,  but  this  is  not  always  easily  seen; 
it  can  be  coaxed  out  by  grinding  a  crystal  of  the  calcite 
to  powder,  wetting  it  with  a  drop  of  water,  and  a  drop 


FLAME,  HEAT  AND   ACID  TESTS.  207 

of  hydrochloric  acid,  then  steeping  in  this  a  few  fibres 
of  asbestus  and  holding  them  in  the  flame. 

2.  Try   fluorite;  it  decrepitates  more   readily  than 
calcite;  it  often  shows   the   calcium    flame    more   dis- 
tinctly than  the    former.     An    interesting    experiment 
with  fluorite  is  the  following:     Heat  an  iron  shovel  al- 
most to  redness;  take  it  into  a  dark  room  and  throw 
some  grains  of  fluorite  on  it;  the  fragments  will  be- 
come   luminous,    shining   with    a   beautiful    bluish    or 
greenish  light  ^this  is  called  phosphorescence.     Apatite 
often    shows   phosphorescence  when  heated;  less   fre- 
quently calcite  and  dolomite. 

3.  Try  gypsum;  see  how   it  turns  white  under  the 
intense  heat.     Wet   it,    heat   it   again,    and    notice    the 
color  of  the  flame ;  gypsum  also  contains  calcium.    After 
you  have  burnt  the  gypsum    white,  you    have   "plaster 
of  Paris." 

4.  Treat  a  scale  of  mica  as    you    did    gypsum,  and 
notice  the  difference. 

5.  Chip  off  a  piece  of  galenite;  notice  the  cleavage. 
Hold  a  very  thin  piece  in  the  flame;  after  it  is  hot,  hold 
it  just  outside  the  edge    of  the  flame    and    admire    the 
delicate  blue  color;  does  it  melt?     Does  it  smell  of  sul- 
phur? 

6.  Try  the  same  with  iron   pyrites;  generally  it  de- 
crepitates; if  the  galenite  did  not   smell  strong  enough 
of  sulphur,  this  will  satisfy  you. 

7.  Orthoclase  after  being  heated  should  show  a  pur- 
ple flame,  because  it  contains  potassium;  if  it  does  not, 
wet  it  with  a  drop  of  HC1,  heat  it  again  near  the  tip  of 


208  THE   WORLD   OF   MATTER. 

the  flame,  then  hold  it  to  the  outer  edge  to  see  the  color. 
[In  many  cases  moistening  the  mineral  with  hydro- 
chloric acid  helps  to  bring  out  the  characteristic  flame. 
A  little  dish  with  a  drop  of  HC1  mixed  with  a  drop  of 
water  is  very  handy  for  this  purpose;  moisten  your 
splinter  or  your  fibres  of  asbestus  by  touching  the  edge 
of  the  drop  with  it]. 

8.  Apatite  will  generally  give  no  characteristic 
color.  Powder  a  little,  wet  with  one  small  drop  of 
sulphuric  acid;  wipe  off  part  of  the  powder  with  a 
little  asbestus  that  has  first  been  heated  in  the  flame  (to 
burn  away  dust  or.  sodium),  then  try  the  flame  test.  It 
will  show  a  brownish  color,  turning  to  bluish  green, 
which  shows  the  presence  of  phosphoric  acid. 

WHAT  CAN    WE    LEARN    FROM    THESE    FLAME    TESTS? 

First — That  certain  minerals,  on  account  of  the  ele- 
ments which  are  in  them,  impart  peculiar  colors  to  the 
flame;  these  are  due  to  the  vapors  which  the  elements 
give  off  when  heated. 

Intense  yellow  flame  (bordering  on  orange)  indicates 
that  sodium  is  present. 

Yellowish-red  flame  indicates  calcium. 

Violet  or  purplish  flame  indicates  potassium. 

Carmine-red  flame  indicates  lithium. 

Crimson  flame  indicates  strontium. 

Emerald-green  flame  indicates  copper  (also  thallium). 

Yellowish-green  flame  indicates  barium  or  boracic 
acid. 

Bluish-green  flame  indicates  phosphorus. 


FLAME,  HEAT  AND   ACID  TESTS.  269 

Azure-blue  (intense)  flame  indicates  selenium. 

Light-blue  flame  indicates  arsenic. 

Copper  in  combination  with  chlorine  gives  also  a 
beautiful  blue  flame.  Dip  a  piece  of  copper  wire  into 
HC1  and  hold  it  in  the  flame;  notice  the  change  from 
azure-blue  to  emerald-green  as  the  chlorine  evaporates. 

The  characteristic  flame  color  of  a  mineral  is  often 
hidden  by  impurities  or  associated  minerals.  Especially 
sodium,  if  present,  makes  it  difficult  to  distinguish  the 
true  color.  If  the  flame  is  viewed  through  blue  glass, 
the  yellow  sodium  flame  is  not  seen.  The  calcium 
flame  is  sometimes  changed  by  the  presence  of  barium 
or  strontium. 

Second — That  some  minerals  melt,  at  least  partly, 
even  in  the  flame  of  an  alcohol  lamp. 

7 hird — That  some  minerals,  especially  those  with 
eminent  (very  perfect)  cleavage,  fly  to  pieces  when 
heated. 

Fourth — That  some  minerals  emit  a  peculiar  odor 
when  heated,  the  most  characteristic  being: 

Sulphurous  odor — most  minerals  containing  sulphur. 

Garlic  odor — minerals  containing  arsenic. 

Horse-radish  (decaying)  odor — minerals  containing 
selenium. 

Bituminous  odor — mineral    hydrocarbons  (coal,  etc.). 

HEAT     TESTS     WITH     THE     OPEN      AND     CLOSED     TUBE. 

Very  small  grains  of  the  minerals  are  generally  best 
for  heat  tests.  To  transfer  them  to  the  tube,  a  little  trough 
made  of  paper  or  tin  is  the  most  convenient  instrument. 


Ho  THE   WORLD   OP  MATTER. 

Cut  a  strip  of  paper  three  or  four  inches  long  and  one- 
eighth  of  an  inch  wide,  arid  double  it  lengthwise;  near 
the  end  of  this  trough  put  the  fragments  or  powder  of 
your  mineral  and  insert  it  in  the  tube;  this  prevents  the 
mineral  from  sticking  to  the  sides  of  the  glass.  Push 
the  paper  into  the  tube  until  your  mineral  fragments 
are  about  half  an  inch  from  the  end,  then  give  the  tube 
half  a  turn,  and  withdraw  the  paper.  See  that  your 
tubes  are  clean  and  dry  inside  and  outside  before  you 
begin  a  test.  . 

HEAT      TESTS      FOR      THE      MINERALS      DESCRIBED      IN 
CHAPTER    XXIII. 

1.  Put  a  few  small  pieces  of  gypsum  into  the  closed 
tube  and  heat  the  closed  end  of  the  tube  in  the  alcohol 
flame;  notice  drops  of  moisture  gathering  in  the  upper 
part  of  the  tube;  heat  until  no  more   moisture  gathers; 
drive  the  water  farther  up  by  heating  the  part  in  which 
it  has  gathered.  This  will  show  that  moisture  is  always 
driven  from   the  hotter  to  the    cooler  part,  evaporating 
in  the  former  and  condensing  in  the  latter.     Pour  out 
the  gypsum;  it  is  white,  and  has  again,  as  before,  been 
changed  by  driving  out  the  water. 

Try  the  same  experiment  with  powdered  talc.  The 
powder  of  limonite  should  be  yellow  or  brown;  notice 
its  color  after  the  water  has  been  expelled.  Try  quartz, 
orthoclase,  and  hematite,  and  see  whether  you  can  drive 
out  any  water.  (Minerals  tying  in  damp  places  some- 
times absorb  some  moisture). 

2.  Try  fluorite,  and  notice  how  it  decrepitates.  Take 


FLAME,   HEAT  AND  ACID  TESTS.  2ii 

xvj»-'.<  r 

the  tube,  after  heating  the  fluorite,  into  a  dark  room 
and  notice  again  the  phosphorescence. 

3.  Put  a  few  grains  of  iron  pyrites  into  the  closed 
tube,  and  heat  it;  a  yellow  coating  of  sulphur  will  form 
on  the  cooler  part;  it  is  driven  out  of  the  pyrite  in  the 
form  of  vapor,  and  it  condenses  again  above,  where  it 
is  cooler;  this  is  called  forming  a  sublimate.  Notice 
the  odor  given  off  while  heated.  Wet  a  narrow  strip 
of  blue  litmus-paper,  and  insert  it  about  one-fourth  of 
an  inch  in  the  tube;  heat  the  mineral  again  and  notice 
the  paper  turning  from  blue  to  red;  this  is  a  sign  that 
acid  fumes  are  escaping.  Try  the  same  with  galena, 
pulverized  finely;  it  takes  stronger  heat  to  drive  the  sul- 
phur off,  but  you  will  notice  the  odor  and  the  acid  re- 
action on  the  litmus  paper.  Of  course,  a  tube  in  which 
sulphur  has  formed  must  not  be  taken  for  another  ex. 
periment  until  all  the  sulphur  is  removed.  You  can 
drive  it  off  by  heat  as  you  did  the  moisture,  but  it  takes 
stronger  heat  and  a  little  skillful  management. 

Fluorite  and  pyrites  should  also  be  tried  in  the  open 
tube.  Insert  a  few  grains  of  the  iron  pyrites,  by  means 
of  your  trough,  in  the  open  tube,  depositing  it  about 
half  an  inch  from  one  end;  hold  the  tube  at  the  other 
end,  slanting,  just  so  that  the  pieces  will  not  fall  out; 
and  hold  the  grains  over  the  flame;  notice  again  the 
sublimate,  the  odor,  which  will  be  stronger  than  before, 
and  the  acid  reaction  on  the  blue  litmus-paper. 

The  difference  between  the  test  in  the  closed  tube 
and  the  open  tube  is  this:  in  the  former  the  substance 
is  heated  without  the  presence  of  oxygen,  because  most 


2ii  THE  WORLD   OF  MATTER. 

of  the  air  is  driven  out  of  the  tube  by  the  heat;  in  the 
latter,  there  is  a  draft  of  air  passing  through  the  tube 
while  the  substance  is  heated,  and  the  vapors  can  unite 
with  the  oxygen  of  the  air.  In  the  case  of  heating 
the  iron  pyrites  in  the  closed  tube,  nearly  all  the  sul- 
phur settles  on  the  cooler  part  of  the  tube,  while  in  the 
open  tube  most  of  it  unites  with  oxygen  and  leaves  the 
tube,  causing  the, strong  odor. 

WHAT    CAN    WE     NOTICE     IN     THE     TESTS     WITH     THE 
CLOSED     AND    OPEN     TUBES? 

The  substance  may  decrepitate;  in  this  case  the  min- 
eral should  be  used  in  the  form  of  powder. 

It  may  give  off  an  odor,  generally  of  the  same  kind 
as  that  noticed  in  the  flame  test,  but  stronger. 

Moisture  may  form  in  the  tube,  which  indicates  that 
the  mineral  contains  water. 

A  coating,  or  sublimate,  may  form  on  the  cool  part 
of  the  tube.  The  following  are  the  most  important: 

A  yellow  coating  indicates  sulphur;  the  odor  will 
prove  it :  brown-red  when  hot,  and  reddish-yellow  when 
cold  indicate  arsenic  sulphide:  brilliant  black,  metallic, 
arsenic,  the  garlic  odor  furnishing  additional  proof: 
black  when  hot,  brown-red  when  cold,  formed  near  the 
mineral  after  strong  heating,  antimony  sulphide:  dark 
red,  selenium  (horse-radish  odor):  a  metallic  mirror, 
composed  of  little  metallic  drops,  mercury  (quicksilver). 

A  few  other  coatings  will  be  mentioned  in  the  de- 
scriptions of  the  minerals  which  produce  them. 

Acid  or  alkaline  vapors  may  be  driven  off;  the  first 


FLAME,   HEAT  AND   ACID  TESTS.  213 

will  redden  blue  litmus-paper,  and  the  second  will  turn 
red  litmus  blue.  The  papers  must  be  moistened. 

A  change  of  color  may  take  place,  as  with  limonite, 
which  changes  into  red  hematite. 

Phosphorescence  is  sometimes  observed. 

»  ACID  TESTS. 

HC1 — Hydrochloric   acid;    H2SOf — Sulphuric  acid. 

For  transferring  the  few  drops  of  acid  needed  from  the 
bottle  to  the  test-tube,  the  dipping-tube,  that  is,  a  nar- 
row glass  tube  about  eight  inches  long,  should  be  used; 
dip  the  tube  about  one  inch  into  the  acid,  and  close  the 
top  with  your  finger;  lift  it  out  and  transfer  it  to  the 
test-tube  which  you  hold  in  your  left  hand,  and  when 
the  lower  part  of  the  dipping-tube  is  near  the  bottom 
of  the  test-tube,  remove  the  finger  and  the  acid  will 
flow  out.  But  first  put  your  mineral — a  few  grains, 
powdered — into  the  test-tube ;  then,  if  the  mineral  is  to 
be  tested  with  diluted  acid,  add  a  few  drops  of  water, 
using  the  dipping-tube;  and  lastly  put  in  the  acid 
Never  put  the  water  into  the  tube  after  the  acid,  always 
before. 

In  heating  the  contents  of  the  test-tube  do  not  apply 
the  bottom  of  the  tube  to  the  flame,  but  hold  it  slant- 
ing and  let  the  upper  part  of  the  liquid  be  nearest  the 
flame;  else  a  steam-bubble,  from  the  bottom,  may  throw 
the  acid  out  of  the  tube.  Heat  gradually.  You  will 
find  it  safer  to  heat  the  acid  by  passing  the  test-tube 
repeatedly  through  the  flame  instead  of  holding  it 
steadily  in  it.  If  the  acid  has  a  tendency  t.o  spurt,  as  it 


214  THE   WORLD   OF   MATTER. 

will  sometimes,  plug  the  opening  of  the  tube  with  a 
light  wad  of  cotton,  or  better,  asbestus.  Do  not  turn 
the  opening  of  the  tube  toward  you.  See  that  the  out- 
side of  your  test-tube  is  dry,  else  it  is  liable  to  crack. 
Have  the  lamp  on  a  slate  or  tray.  You  can  use  the 
tube-holder  with  the  test-tube,  but  experts  use  their 
ringers. 

EXPERIMENTS    WITH    ACIDS. 

After  having  read  the  foregoing  directions  carefully, 
you  may  begin  to  test  your  specimens. 

i.  Powder  a  fragment  of  calcite  and  transfer  to  the 
bottom  of  the  test-tube;  dip  the  dipping-tube  an  inch 
into  water,  then  close  the  top  with  your  finger  and 
transfer  the  water  into  the  test-tube.  Do  the  same  with 
HC1.  Do  not  let  the  liquids  flow  down  the  side 
of  the  test-tube,  but  deposit  them  just  above  the 
powdered  mineral.  Notice  the  effervescence  or  bubbling 
up  of  gas.  Put  a  drop  of  acid  on  the  piece  of  calcite 
and  see  again  the  effervescence ;  if  you  have  a  piece  of 
marble,  try  it  on  that.  See  whether  the  acid  will  have 
the  same  effect  on  any  other  mineral  in  your  collection.. 
Thus  we  have  an  easy  method  for  determining  calcite  or 
limestone.  After  the  calcite  is  all  dissolved,  heat  the 
solution  to  concentrate  it;  then  put  a  drop  on  the 
smooth  side  of  your  streak-plate,  or  any  other  piece  of 
glass;  also  put  a  drop  of  pure  HC1  on  the  glass,  and 
let  both  dry;  examine  both  drops;  of  the  HC1  very 
little  is  left;  of  the  calcium  chloride,  which  was  in  the 
first  drop,  you  may  see  the  crystals  with  a  magnifying 
glass.  The  glass  plate  should  be  slightly  warmed. 


FLAME,  HEAT  AND   ACID   TESTS.  215 

2.  Powder  a  little  fluorite  and  put  it  into  a  test-tube; 
examine  the  tube  first  to  see  whether  it  is  perfectly 
clean  and  clear,  especially  near  the  bottom. 

Put  in  a  few  drops  of  H2SO4,  not  diluted  with 
water;  heat  slowly  and  carefully;  do  not  smell  the 
fumes  in  this  test;  they  are  poisonous.  When  the  acid 
is  nearly  evaporated,  let  the  tube  cool,  then  wash  it  out 
with  water  and  let  it  dry;  you  will  find  that  the  glass 
has  been  attacked  (corroded)  by  the  fluorite. 

Another  test:  Put  a  little  powdered  fluorite  on  the 
smooth  side  of  your  streak-plate;  let  one  drop  of  sul- 
phuric acid  fall  on  it;  put  the  plate  away  in  a  safe  place 
over  night,  wash  away  the  acid  and  powder  and  notice 
the  effect  on  the  glass.  These  are  tests  to  detect  the 
presence  of  fluorine  in  a  mineral. 

WHAT    HELP     CAN     WE     GET     FROM     THE     ACID     TESTS 
TO    DETERMINE    MINERALS? 

Some  minerals  dissolve  with  effervescence  in  diluted 
HC1,  especially  the  carbonates,  as  carbonate  of  calcium 
(limestone),  carbonate  of  iron  (siderite),  and  others. 

Some  minerals  dissolve  without  effervescence. 

Some  minerals  dissolve  partly  or  sparingly. 

The  substance  formed  by  the  solution  may  be  found 
by  evaporating  the  liquid.  It  will  generally  crystallize; 
the  crystals  cannot  always  be  seen  by  the  naked  eye,  but 
the  student  possessing  a  microscope  will  find  a  source 
of  great  delight  in  their  examination. 


2i6  THE   WORLD   OF   MATTER. 


CHAPTER  XXV. 

TWELVE    OTHER    MINERALS. 

We  will  now  examine  twelve  other  common  miner- 
als. (Specimens  Nos.  8,  10,  16,  17,  18,  21,  22,  25,  27, 
34,35,  and  36.) 

Determine  these  if  possible  by  an  examination  of 
their  physical  properties.  Afterward  use  the  flame, 
heat,  and  acid  tests  to  identify  any  not  recognized  by 
their  external  characteristics,  and  to  verify  your  de- 
cisions with  regard  to  the  others. 

It  is  a  good  plan  to  enter  in  a  blank  book  the  obser- 
vations made  on  each  specimen  as  it  is  tested.  Com- 
pare your  descriptions  with  those  that  follow. 

Abbreviations:  H. — hardness;  fl. — flame  test;  c.t. 
— closed  tube;  o.t. — open  tube;  comp. — composition; 
b.b. — before  the  blowpipe. 

Italics  indicate  important  characteristics  which  will 
help  you  distinguish  a  mineral  from  others  that  more  or 
less  closely  resemble  it. 

DESCRIPTION  OF    THE    SECOND    DOZEN    MINERALS. 

i.  Sulphur. — H.,  2;  lustre,  resinous;  color,  yellow 
to  gray  or  brown ;  streak,  yellow ;  translucent  to  opaque ; 
generally  massive,  sometimes  crystallized,  also  stalactitic; 
fracture,  uneven ;  very  brittle;  light. 

Comp.— S., — Fl.,  burns  with  a  blue  flame  and  sulphur- 


TWELVE"  OTHER   MINERALS.  217 

ous  odor,  and  melts;  c.  t.,  melts,  then  vaporizes,  the 
vapor  forming  a  coating  on  the  cooler  part  of  the  tube. 
When  the  mineral  is  held  in  the  warm  hand  a  crackling 
noise  is  heard.  It  becomes  electric  when  rubbed. 

2.  Stibnite (gray antimony). — II.,  2.5;  lustre,  metal- 
lic; color,  lead-gray;  streak,  gray;  opaque;  crystalline; 
columnar  or  fibrous  to  massive  granular;  cleavage,  per- 
fect to  indistinct;  brittle;  rather  heavy. 

Comp. — Sb2S3  (antimony  sulphide). — Fl.,  bluish, 
decrepitates,  melts ,  sulphur  odor;  c.  t.,  decrepitates, 
melts,  acid  reactions  on  litmus  paper;  o.  t.,  fills  the  tube 
with  white  fumes,  characteristic  of  ores  of  antimony 
and  which  leave  a  white  coating;  peculiar  odor  in 
which  sulphur  can  readily  be  detected.  As  the  frag- 
ments decrepitate  violently,  they  should  be  finely  pow- 
dered for  this  test.  HC1,  dil.;  generates  sulphuretted 
hydrogen,  marked  by  its  disagreeable  odor.  Stibnite 
is  named  from  stibium,  the  scientific  name  for  the  ele- 
ment antimony.  Stibnite  is  easily  recognized  on  ac- 
count of  its  melting  so  readily. 

3.  Sphalerite    (zinc    blende,   Black     Jack).—H., 
nearly  4;   lustre,  resinous  or  metallic;  color,  yellow  to 
red.  brown,  and  grayish;  streak,  yellowish  white;  trans- 
lucent   to    opaque;  crystalline,    sometimes  granular    to 
nearly    compact;     cleavage,    perfect;     brittle;     rather 
heavy. 

Comp — ZnS,  (zinc  sulphide). — FL,  does  not  melt; 
sulphur  odor;  c.  t.,  acid  reaction.  HC1  evolves  sul- 
phuretted hydrogen,  especially  when  heated.  Sphaler- 
ite comes*  from  a  Greek  word  meaning  treacherous. 


2x8  THE  WORLD   OF  MATTER. 

The  German  word  blende  means  deceiving;  it  is  often 
found  together  with  galena,  but  yielding  no  lead,  the 
miners  thought  a  trick  had  been  played  on  them  by  the 
goblins.  It  is  now  an  important  source  of  zinc. 

4.  Cryolite. — H.,  3;    lustre,   vitreous;    colorless    to 
white   and   brownish;    streak,   white;    transparent    to 
translucent;     usually    massive;     cleavage   not    always 
distinct;  brittle,  light. 

Comp. — Na6Al2F12;  FL,  yellow  soda  flame;  melts 
in  the  hot  part  of  the  flame.  This  test  affords  an  easy 
distinction  between  this  mineral  and  others  that  resemble 
it  in  color  and  lustre;  take  a  small  splinter  for  the  test. 
C.  t.  decrepitates;  acid  reaction;  etches  the  glass  a  little 
above  the  point  where  it  is  heated.  Try  the  tests  for 
fluorine.  Cryolite  is  used  for  making  soda,  the  metal 
aluminum,  and  a  white  glass.  Siderite  frequently  ac- 
companies cryolite.  Cryolite  means  ice-stone;  this 
name  is  given  to  it  because  it  melts  easily. 

5.  Limonite. — H.,  about  5 ;  streak,  yellow  to  brown ; 
lustre  sub-metallic  to  silky;  color,  yellow  or  brown; 
brittle;  cleavage,  uneven,  splintery. 

Comp. — 2  Fe2O3  -f-  3  H2O;  c.  t.  yields  water  which 
condenses  in  upper  part  of  tube.  Compare  the  streak 
of  limonite  with  the  streak  obtained  by  rubbing  a  rusted 
bar  of  iron  on  paper.  It  is  reasonable  to  conclude  from 
the  close  similarity  of  the  streaks  that  we  have  in  this 
limonite  iron-rust  or,  what  is  the  same  thing,  iron  oxide 
— iron  combined  with  oxygen  taken  from  the  air.  The 
name  limonite  is  derived  from  a  word  meaning  a  mead- 
ow or  swamp,  and  is  used  because  this  "bog-iron-ore"  is 


TWELVE    OTHER   MINERALS.  219 

formed  in  wet  places.  Test  the  streak  of  limonite  after 
it  has  been  heated  in  the  closed  tube:  it  is  now  red,  not 
yellow.  Compare  it  with  the  streak  of  hematite;  it  has 
the  same  appearance.  In  fact  hematite  is  exactly  like 
limonite  from  which  the  water  has  been  expelled  by 
heat. 

Neither  ore  is  attracted  by  a  magnet.  Limonite  and 
hematite  are  the  two  great  natural  coloring  agents.  Al- 
most all  the  yellow,  brown,  and  red  colors  in  rocks  and 
soils  are  due  to  them. 

6.  Chlorite. — H.,  about  2;    lustre,   pearly   to  dull; 
streak,    light    green;     color,   dark    green;    clay    odor 
noticed  when  the  specimen  is  breathed  upon;  generally 
somewhat  greasy  to  the  touch. 

Comp. — Chlorite  is  properly  the  name  of  a  group  of 
highly  basic  minerals  of  variable  composition,  but  all 
essentially  hydrous  silicates  of  aluminum,  magnesium 
and  iron.  The  specimen  in  this  collection  is  prochlorite, 
one  of  the  most  abundant  species.  It  yields  water  in 
the  closed  tube. 

7.  Celestite. — H.,  4;  lustre,   vitreous  to  pearly ;  col- 
orless, white,  generally  with  a  bluish  tint,   also  yellow- 
ish; streak,  white;  transparent   to   translucent;  crystal- 
line, brittle. 

Comp. — SrSO4,  (strontium  sulphate):  Fl.  decrepi- 
tates slightly.  The  characteristic  flame  is  a  deep  crim- 
son red\  but  it  is  difficult  to  get  it  in  the  alcohol  flame 
without  the  use  of  the  blow-pipe;  you  will  succeed, 
however,  in  coaxing  it  out  by  treating  it  in  the  follow- 
ing manner: 


220  THE  WORLD   OF   MATTER. 

Grind  a  small  fragment  to  a  fine  powder;  take  some 
fibres  of  asbestos,  dip  them  in  the  powder  and  hold 
them  with  the  forceps  in  the  edge  of  the  blue  flame;  a 
yellowish  flame  generally  appears  at  first,  but  after  con- 
tinued heating,  especially  by  holding  it  for  a  little  while 
in  the  hottest  part  of  the  flame,  the  color  will  turn  to  a 
reddish  hue;  now  slightly  moisten  the  tip  of  your  as- 
bestos with  HC1  (by  holding  it  just  at  the  edge  of  a 
drop  of  the  acid)  introduce  into  the  flame  again  and 
notice  the  crimson  flashes.  Keep  it  in  the  flame  for  a 
little  while;  if  the  color  is  not  distinct,  repeat  the  test. 

Celestite  is  derived  from  the  latin  word  for  skj,  be- 
cause the  mineral  is  sometimes  blue;  preparations  made 
from  this  mineral  are  used  for  the  crimson  lights  in  fire- 
works. 

8.  Kaolinite. — H.,    i  to  2;  color,  white  when  pure, 
(then  used  to  make  porcelain)   but   generally  yellowish 
or  gray;  streak,  same  as  color;  lustre,   none,  i.e.  dull; 
friable,  (crumbling  between  the  finger).     A  yellowish 
clay. 

Comp. — Al2Si.,O7  +  2H2o.  Infusible  and  insoluble. 
C.t.  yields  water. 

9.  Hornblende.  —  (amphibole). —  H.,    5J;      streak, 
white;  color,  greenish  to  black;  lustre,  silky  to  vitreous, 
reminding    one    of    the    lustre     of    feldspar;     brittle, 
cleavage,  prismatic,  perfect. 

Comp. — (Ca  Mg  Al  Fe)Si  O3.    Insoluble,  infusible. 

10.  Labradorite. — H.,  6;  lustre,    vitreous  to  pearly, 
feldspar  lustre;    color,  generally   light   and  dark  gray 
mixed:  streak,  white;  translucent;   generally  massive j 


TWELVE   OTHER   MINERALS.  221 

cleavage,  perfect  to  interrupted;  brittle.  Labradorite 
often  shows  a  beautiful  play  of  colors  if  viewed  at  a 
certain  angle,  (especially  in  the  dark  gray  portions) ; 
blue  and  green  are  the  more  common  colors;  yellow 
and  red  are  rare.  The  color  is  generally  seen  best  on 
wetting  the  specimen.  Labradorite  is  a  variety  of  feld- 
spar (soda-lime  feldspar);  it  is  generally  darker  and  a 
little  heavier  than  the  other  varieties.  It  is  named  from 
Labrador,  where  fine  specimens  have  been  obtained. 

Comp.— (Na2Ca)Al2Si3O1 0.     Insoluble. 

ii.  Biotite,  (J)lack  mica). — H.,  nearly  3;  lustre, 
pearly  to  sub-metallic;  color,  black,  or  nearly  so;  streak, 
gray;  translucent  to  opaque;  crystalline,  foliated; 
cleavage,  perfect,  sectile.  The  thin  leaves  into  which 
it  splits  are  elastic. 

Comp. — (K  FeMgAl)2SiO4,  (potassium-iron-mag- 
nesiiim-aluminum  silicate):  Fl.,  the  purple  potash 
flame  is  often  noticed.  Put  a  few  small  scales  into  a  test 
tube,  add  about  10  drops  of  H2SO4  (undiluted),  and  heat 
carefully;  the  mineral  will  partly  dissolve;  pour  off  the 
acid,  leaving  what  remains  of  the  mineral  in  the  tube, 
fill  the  tube  with  water  to  wash  out  the  remaining  acid 
and  examine  what  is  left  of  the  scales;  they  have 
changed  from  black  to  white  and  now  consist  simply 
of  the  silica,  which  remains  undissolved.  Muscovite 
does  not  dissolve  in  H0SO4.  '  Between  Muscovite  and 
Biotite  there  is  another  variety  of  mica  called  Phlogo- 
pite.  (/.  <?.,  having  a  fiery  appearance);  it  is  generally  of 
a  bronze  lustre;  it  also  dissolves  in  H2SO4.  Biotite  is 
named  after  the  French  mineralogist  Biot. 


$12  THE   WORLD   OF   MATTER. 

12.  Chrysotile. — H.,  3. 75;  lustre,  silky;  generally 
greenish,  but  also  light  gray,  yellow  to  brown;  streak, 
white;  translucent;  crystalline,  fibrous,  separates  into 
fine,  flexible  fibres. 

Comp. — Mg2SiO4+H2O,  (hydrous  magnesium  sili- 
cate): Fl.  does  not  melt,  but  becomes  brittle,  c.  t.  yields 
considerable  water.  Chrysotile  is  a  fibrous  variety  of 
serpentine;  it  is  commonly  called  asbestos,  and,  indeed, 
it  resembles  this  mineral  very  closely,  and  is  used  for  the 
same  purposes  for  which  asbestos  is  used,  that  is,  for 
making  fire-proof  cloth,  paper  and  ropes,  coverings 
for  boilers,  etc.  Very  fine  silky  varieties  of  asbestos 
and  chrysotile  are  called  amianthus.  The  name,  chry- 
sotile,  means  golden  fibre.  Asbestos  is  a  variety  of  am- 
phibole,  and  the  name  means  indestructible.  Its  compo- 
sition is  generally  (Ca  Mg  Fe)  Si  O3. 

WHAT    THE    TESTS    MEAN. 

Compounds  are,  as  a  rule,  so  different  from  the  elements 
of  which  they  consist,  that  it  is  often  impossible  to  tell, 
by  looking  at  a  mineral,  of  what  it  is  composed.  There- 
fore, some  means  are  resorted  to  to  separate  or  decom- 
pose the  compound,  so  that  we  can  detect  some  well- 
known  and  prominent  property  of  the  elements.  This 
examination  of  a  substance  is  called  analysis.  If  we 
wish  simply  to  know  whether  a  certain  element  is  pres- 
ent in  the  compound  we  make  a  partial  analysis;  if  we 
wish  to  know  every  element  that  is  present,  we  must 
make  a  qualitative  analysis,  and  if  we  wish  to  find 
exactly  how  much  (what  percentage)  of  one  or  all  the 


TWELVE   OTHER    MINERALS.  223 

elements    is    present,   we    must    make   a    quantitative 
analysis. 

ANALYSIS    IN    THE    DRY    WAY. 

Flame  tests. — Heat  decomposes  nearly  all  com- 
pounds. In  the  flame  tests,  part  of  the  mineral  becomes 
decomposed  and  vaporizes,  and  those  elements  whose 
burning  vapor  has  a  characteristic  color  or  odor,  as  the 
yellow  of  sodium,  the  orange  of  calcium,  the  emerald 
green  of  copper,  the  odor  of  sulphur,  arsenic,  etc.,  can 
be  detected. 

The  tests  in  the  tubes. — Heat  is  used  also  in  these 
tests  to  decompose  the  compounds;  sometimes  we  find 
the  elements  separated  in  different  parts  of  the  tube,  as 
we  noticed  in  testing  iron  pyrites,  when  sulphur  and  iron 
were  separated.  Sometimes  the  acid-element  is  driven 
off,  and  reveals  itself  by  the  smell,  and  by  the  change 
of  the  color  of  litmus-paper;  or,  in  the  case  of  an  oxide, 
the  oxygen  may  be  driven  off.  In  heating  limonite, 
the  water  is  expelled,  changing  the  hydrous  yellow 
substance  to  anhydrous  red  hematite. 

EXAMINATION    IN    THE    WET    WAY. 

The  chemical  power  which  holds  the  different  elements 
in  a  compound  together,  becomes  weaker  also  through 
solution.  Few  minerals  dissolve  readily  in  water,  but 
quite  a  number  in  HC1,  H2SO4  or  HNO3  (nitric  acid). 
When  a  mineral  dissolves  in  an  acid  it  unites  with  a 
part  of  the  acid  and  forms  a  new  compound.  Zinc,  for 
instance,  dissolves  in  chlorhydric  acid,  and  becomes 


124  THE   WORLD   OP  MATTERS 

chloride  of  zinc.  If  there  is  already  an  acid  element  in 
the  mineral,  a  stronger  acid-element  will  drive  it  out 
and  take  its  place.  Calcite,  CaCO3  is  calcium  com- 
bined with  the  CO3  part  of  carbonic  acid,  H0CO3; 
HG1  is  stronger  than  carbonic  acid,  it  drives  out  the 
CO3  and  combines  with  the  calcium,  forming,  instead 
of  a  carbonate,  a  chloride  of  calcium.  The  chemist  puts 
it  down  in  this  way : 

CaC03+2HCL=CaCl8+C08+H8O. 

What  becomes  of  the  CO3  ?  CO2  escapes  in  bub- 
bles, causing  the  effervescence.  The  other  O  unites 
with  the  2H  left  from  the  2HC1  and  forms  H2O 
(water)  which  remains  in  the  test  tube. 

Calcium  chloride  is  soluble  in  water,  like  common 
salt.  If  we  wish  to  get  it  in  its  solid  form  we  must 
evaporate  the  solution. 

In  applying  the  acid  tests  the  following  facts  are 
worth  remembering: 

An  acid  may  form,  with  the  mineral,  a  soluble  com- 
pound. Then  the  solution  is  clear;  there  is  no  sedi- 
ment left  after  all  is  dissolved,  as  we  saw  in  dissolving 
calcite  in  HCL 

An  acid  may  form  an  insoluble  compound;  a  precipi- 
tate will  then  be  formed,  as  in  treating  calcite  or  calcium 
chloride  with  H2SO^. 

An  acid  may  dissolve  a  part  of  a  mineral,  as  in  the 
case  of  biotite. 

An  acid  may  have  no  effect,  the  mineral  being  insolu- 
ble, as  quartz. 


TWELVE   OTHER   MINERALS.  22$ 

In  dissolving  (or  combining)  minerals  with  HC1  you 
change  them  to  chlorides;  with  HNO3  to  nitrates; 
with  H2SO4  to  sulphates. 

Carbonates  will  effervesce  with  HC1  (and  other 
stronger  acids)  some  with  the  cold  acid,  others  only 
with  the  hot  acid. 


226  THE   WORLD  OF  MATTER- 


CHAPTER  XXVI. 

BLO\T-PIPE     ANALYSIS. 

The  analysis  of  many  m'neral  compounds  requires  a 
greater  heat  than  that  of  an  alcohol  lamp.  This  is 
obtained  by  means  of  the  blow-pipe,  a  simple  instru- 
ment by  which  a  strong  current  of  air  is  added  to  the- 
flame  of  a  lamp  or  gas-jet,  increasing  its  heat  by  a 
freer  supply  of  oxygen,  and  at  the  same  time  directing 
and  concentrating  the  flame  upon  the  specimen. 

A  simple  curved  brass  blow-pipe,  costing  20  cents, 
answers  the  purpose.  A  stearine  candle,  with  a  thick 
wick,  furnishes  a  good  flame ;  but  a  properly  arranged 
Bunsen  burner  is  better.  Fig.  28K- 

Charcoal  is  generally  used  as  a  support  for  the  sub- 
stances to  be  heated.  It  is  best  to  buy  the  coal  which 
is  specially  prepared  for  this  purpose. 

Platinum  wire  and  foil  must  be  on  hand.  Platinum 
makes  excellent  instruments  for  holding  specimens  in 
the  blow-pipe  flame,  because  it  does  not  melt. 

The  wire,  No.  27,  is  cut  into  pieces  about  two  inches 
long.  These  should  be  fitted  with  wooden  or  glass 
handles.  Hold  the  end  of  a  small  glass  tube,  two 
inches  long,  in  the  Bunsen  flame,  turning  it  as  it  grows 
hot.  As  the  glass  softens,  the  opening  in  the  tube 
grows  smaller;  when  just  large  enough  to  admit  the 


BLOW-PIPE    ANALYSIS. 


platinum  wire,  insert  about  a  quarter   of    an  inch   of  it 
into  the  tube,  and  finish  melting  it  together. 

Bend  the  free  end  of  the  wire  into  a  round  loop,  an 
eighth  of  an  inch  in   diameter,  and  you  have  a  service 


able  little  instrument.  A  forceps  with  platinum  points 
is  so  convenient,  as  well  to  repay  its  cost. 

Care  must  be  taken  not  to  use  any  platinum  instru- 
ments for  testing  lead,  tin,  zinc,  or  other  easily  fusible 
ores,  for  they  make  an  alloy  with  platinum,  and  render 
it  easily  destructible. 

Lay  a  sheet  of  paper  under  the  lamp  or  burner  before 
beginning  work.  It  will  catch  fragments  dropped  dur- 


THE   WORLD   OF  MATTER. 


ing  the  examination.     Record  all  observations  in  a  note- 
book. 

You  must  learn  to  blow  a  continuous  blast  through 
the  blow-pipe,  while  breathing  naturally.  This  is  ac- 
complished by  inflating  the  cheeks  and  allowing  them 
to  contract,  expelling  the  air  while  you  are  drawing  in 
your  breath.  It  is  difficult  at  first,  and  you  should  get 
some  one  to  show  you  how  to  do  it  if  possible. 

Hold  the  tip  of  the  blow-pipe  in  the  middle  of  the 
flame,  just  above  the  wick,  if  you  use  an  alcohol  lamp 
or  a  candle;  do  not  push  it  quite 
so  far  into  the  flame  of  a  Bunsen 
burner.  Blow  gently,  so  as  to 
cause  the  flame  to  taper  away 
from  the  blow-pipe  to  a  fine  point. 
The  brightness  of  the  flame 
should  disappear,  and  you  should 
observe  a  fine  blue  cone  sur- 
rounded by  a  very  faint  flame. 
When  you  can  produce  this 
flame  and  maintain  it  steadily  for 
several  minutes,  blowing  from 
the  cheeks  and  not  from  the  chest, 
you  have  mastered  the  art  of 
blowing.  Fig.  29  represents  a 
candle  flame,y  is  the  dark  central 
portion  filled  with  gases  formed  from  the  heated 
stearine;  a  b  c  is  the  brilliant  flame  where  the  com- 
bustion is  incomplete,  and  the  particles  of  carbon  are 
incandescent;  a  e  c  is  the  faint  outer  flame  caused  by  the 


Fig.  29. 


BLOW-PIPE   ANALYSIS. 


229 


complete  combustion  of  the  carbon  with  hydrogen  and 
cxygen.  Upon  introducing  the  blow-pipe  and  blowing 
gently,  the  flame  takes  the  position  shown  in  Fig.  30. 

The  increased  supply  of 
oxygen  causes  more  perfect 
combustion,  as  shown  by 
the  disappearance  of  the 
brilliant  flame,  and  the  for- 
mation of  the  blue  cone,  sur- 
rounded by  a  still  fainter 
conical  flame  which  extends 
beyond  it. 

Substances  held  just  be- 
yond the  blue  cone  in  this 
faint  outer  flame  are  heated  in  contact  with  the  oxygen 
of  the  air,  and  many  metals  thus  become  oxidized. 

This  outer  flame  is 
therefore  called  the 
oxidizing  flame. 

If    the    tip    of    the 
blow-pipe  is  held  just 
outside  the  flame,    and 
the    flame   gently  di- 
rected     outward    and 
downward,  Fig.  31  the 
flame  keeps  its  yellow 
colors,  and  if  an  oxide 
of  a  metal  is  held  in  the  end  of  this  flame  it  becomes 
partly  or  entirely  deoxidized  or  reduced. 
This  then  is  the  reducing  flame.* 


230  THE   WORLD    OF   MATTER. 

O.  F.  stands  for  "oxidizing  flame."  This  flame  is 
used  not  only  for  changing  metals  or  their  compounds 
into  oxides,  but  also  to  test  the  fusibility  of  minerals. 
The  hottest  part  is  the  tip  of  the  blue  cone. 

R.  F.  stands  for  "reducing  flame."  It  is  chiefly  used 
to  separate  the  metals  from  their  compounds. 

The  Bunsen  flame  should  be  about  an  inch  and  a  half 
^igh  for  the  O.  F.,  and  half  an  inch  higher  for  the  R.  F. 

FIRST    EXPERIMENTS. 

Direct  the  O.  F.  upon  a  splinter  of  cryolite. 

Observe  how  readily  it  melts.  Try  a  small  splinter 
of  celestite.  It  fuses,  though  less  readily,  and  shows  its 
characteristic  crimson  flame.  Place  a  drop  of  water  on 
red  litmus-paper,  and  dip  into  it  the  fused  splinter  of 
celestite;  notice  that  the  litmus  turns  blue.  What  does 
this  indicate? 

Now  try  to  melt  a  fragment  of  quartz.  If  you  can 
melt  it  in  the  slightest  degree  you  perform  a  feat  hith- 
erto deemed  impossible. 

Try  next  a  bit  of  galenite.  In  the  platinum  forceps? 
Not  unless  you  wish  to  ruin  the  instrument! 

Make  a  slight  excavation  in  a  piece  of  charcoal  about 
half  an  inch  from  the  end ;  in  this  place  the  galenite  and 
direct  the  tip  of  the  O.  F.  upon  it.  Stop  occasionally  to 
observe  the  coating  formed  on  the  coal,  and  to  smell  the 
fumes  that  arise.  Notice  that  the  color  of  the  coating 
near  the  specimen  quickly  changes  from  orange  to  light 
yellow  as  you  remove  the  coal  from  the  flame,  and  that 
it  grows  still  lighter  as  it  gets  cold.  Galenite,  you  re- 


BLOW-PIPE  ANALYSIS.  231 

member  is  lead  sulphide.  Some  of  the  sulphur  has 
volatilized,  combining  with  oxygen  to  form  the  odorous 
fumes.  Some -of  the  lead  has  united  with  oxygen,  form 
ing  the  yellow  oxide  deposited  near  the  specimen  or 
assay ;  another  part  of  the  lead  has  been  changed  into 
lead  sulphate,  and  is  deposited  farther  away  on  the 
cooler  portion  of  the  coal.  Upon  the  remainder  of  the 
assay  direct  now  the  R.  F.,  until  a  bright  little  drop,  or 
globule  is  formed.  Let  this  drop  on  a  piece  of  asbestus 
paper,  or  let  it  cool  on  the  coal. 

It  is  no  longer  brittle  galenite,  but  malleable  lead, 
as  you  can  prove  by  a  blow  of  a  hammer. 

These  simple  experiments  have  shown  the  use  of  the 
biovv-pipe : 

To  test  the  fusibility  of  minerals; 

To  exhibit  colors  imparted  to  the  flame; 

To  oxidize  and  to  reduce  metals; 

To  cause  the  formation  of  coating;  or  sublimates,  on 
charcoal— often  an  important  aid  in  determining  a  min- 
eral. 

DEGREES     OF    FUSIBILITY. 

We  may  call  very  easily  fusible. — Minerals  whose 
fragments  melt  in  the  alcohol  or  gas  flame  without  a 
blow-pipe;  as  stibnite,  and  halite.  Fusibility  i. 

Easily  fusible. — Minerals  that  melt  in  the  blow-pipe 
flame  in  fragments  as  large  as  a  grain  of  wheat;  as 
pyrites.  Fusibility  2. 

Fusible. — Minerals  melting  less  readily,  but  still 
visibly  affected  in  fragments  as  large  as  wheat  grains; 
as  celesute.  Fusibility  3. 


r,32  THE   WORLD   OF   MATTER, 

fusible  with  difficulty. — Minerals  that  fus^  only  in 
very  small  splinters;  as  most  varieties  of  hornblende. 
Fusibility  4. 

Almost  infusible. — Minerals  that  are  rounded  only 
on  the  sharp  points,  and  edges  of  minute  splinters,  after 
long  and  strong  heating,  as  orthoclase.  Fusibility  5. 

Infusible. — Minerals  not  affected  by  flame;  as  quartz. 
Fusibility  6. 

"All  the  minerals  named  above  are  included  in  the  col- 
lection accompanying  this  book,  and  you  should  become 
familiar  with  their  action  before  the  blow-pipe  before 
attempting  others. 

Other  phenomena  than  fusing  are  sometimes  observed 
when  blow-piping,  e.  g.  swelling,  branching,  decrepita- 
ting, brightly  glowing  (especially  lime,  strontia,  zinc, 
and  tin).  Careful  notes  should  be  made  of  everything 
observed. 

EXAMINATION    ON    CHARCOAL. 

Easily  fusible  metals  must  be  examined  on  char- 
coal, as  we  saw  in  the  case  of  galenite.  If  the  speci- 
men decrepitates  so  strongly  as  to  fly  to  pieces  when 
touched  by  the  flame,  powder  it.  Moisten  with  a  dl  op 
of  water  as  much  of  the  powder  as  you  can  take  on 
the  point  of  your  knife-blade,  mix  to  a  paste,  and  place 
the  mass  in  a  little  excavation  made  near  the  end  of  the 
charcoal.  In  directing  the  flame  upon  the  assay  blow 
gently  until  the  moisture  is  expelled. 

Try  stibnite.  It  fuses  readily,  imparting  a  greenish 
hue  to  the  flame,  and  yielding  dense  white  fumes  which 
f  prm  a  white  coating  on  the  coal, 


BLOW-PIPE  ANALYSIS.  233 

Touch  this  coating  with  the  tip  of  the  R.  F.  and  it 
disappears,  again  tinging  the  flame  with  green.  This 
proves  that  the  sublimate  of  antimony  oxide  is  volatile. 

Try  sphalerite.  The  fragment  does  not  fuse,  though 
it  may  form  a  yellow  coating  near  the  assay,  turning 
white  as  it  cools. 

You  remember  that  when  limonite  was  heated  in  a 
closed  tube  a  large  quantity  of  water  was  driven  off, 
and  the  mineral  afterward  had  the  appearance  of  hema- 
tite. Repeat  the  experiment  with  the  blow-pipe.  The 
same  result  is  produced  more  quickly  under  the  intenser 
heat.  Do  not  stop  this  time  when  the  limonite  has  been 
reduced  to  hematite;  continue  the  heating,  and  observe 
lhat  the  assay  grows  still  darker,  and  at  last  partially 
fuses.  Test  it  now  with  a  magnet.  Unlike  both  limo- 
nite and  hematite,  it  is  attracted. 

Yet  it  is  not  pure  iron,  for  a  smart  blow  of  the  ham- 
mer crumbles  it  to  powder.  It  is  reduced  to  that  com- 
pound of  iron  called  magnetite,  specimen  1 2.  It  is  be- 
lieved that  this  series  of  iron  ores  has  been  formed,  in 
nature,  on  the  same  principle  which  has  been  illustrated 
in  our  experiments;  i.  £.,  limonite,  deposited  in  the  earth 
from  a  solution  of  iron,  has  afterward  been  converted 
into  hematite  by  heat,  and  hematite  has  in  the  same  way 
been  reduced  to  magnetite. 

Test  now  a  few  grains  of  iron. rust,  which  you  can 
scrape  from  an  old  stove-pipe,  or  other  iron.  Does  its 
streak  resemble  limonite?  It  is  practically  the  same 
mineral.  What  are  the  results  of  heating  it?  Test  the 
assay,  after  heating,  with  a  rc.ajgjnet. 


234  THE   WORLD   OF  MATTER 

Repeat  the  experiment  of  burning  iron  in  oxygen. 
Test  with  the  blow-pipe  a  fragment,  or  some  powder, 
of  the  resulting  black  oxide  of  iron.  Test  it  with  the 
magnet  before  and  after  heating. 

REAGENTS. 

We  have  frequently  used  litmus-paper  in  order  to  de- 
tect an  acid  or  an  alkaline  reaction ;  a  change  of  color 
from  blue  to  red  indicating  the  presence  of  an  acid ; 
while  minerals  containing  as  their  base  calcium,  stron- 
tium, barium,  or  magnesium  all  have  the  same  alka- 
line reaction  after  being  strongly  heated  which  we  ob- 
served in  the  case  of  celestite. 

Cobalt  is  a  reddish-white  metallic  element,  of  no 
special  utility,  except  for  the  brilliant  colors  that  are  ob- 
tained from  its  various  compounds.  To  glass  these  com- 
pounds impart  a  magnificent  tint  which  is  easily  recog- 
nized as  cobalt  blue.  With  other  substances  than  glass 
other  colors  are  produced,  so  that  by  the  color  obtained 
by  moistening  different  minerals  with  a  solution  of  some 
cobalt  compound  and  then  heating  them  it  is  often  pos- 
sible to  determine  their  nature  and  their  names. 

The  most  convenient  preparation  of  cobalt  for  this 
purpose  is  a  solution  of  one  dram  of  the  nitrate,  Co 
(NO3)  2,  in  an  ounce  of  water. 

Heat  another  fragment  of  sphalerite  on  charcoal  un- 
til you  obtain  the  yellow  coating  or  sublimate  on  the 
coal  next  to  the  assay.  Put  a  drop  of  the  cobalt  so- 
lution on  the  sublimate,  and  also  upon  the  assay,  if  that 
has  changed  to  a  light  color  through  heating.  Direc* 


BLOW-PIPE  ANALYSIS.  235 

the  O.  F.  again  upon  the  assay;  when  cool,  the  subli- 
mate or  part  of  it,  and  probably  also  the  assay,  will  be 
bright  green. 

If  you  fail  to  get  any  coating  or  sublimate  by  simply 
heating  the  sphalerite,  pulverize  a  fragment  in  the  mor- 
tar, mix  the  powder  in  the  palm  of  your  hand  with  an 
equal  quantity  of  pure  sodium  carbonate, — or  of  ordi- 
nary baking  soda  if  free  from  sulphur — moisten  the 
mixture  and  expose  it  to  the  O.  F.  It  will  melt  and  run 
together,  but  after  a  time  will  spread  out  again  and  sink 
into  the  coal.  Keep  playing  upon  it  with  the  hot  point 
of  the  flame  until  you  have  a  distinct  coating  beyond 
the  assay ;  then  treat  with  the  cobalt  solution  as  before. 
Repeat  this  test  with  all  the  ores  of  zinc  you  may  have. 
You  should  keep  a  small  bottle  of  this  cobalt  solution 
on  hand.  Always  make  the  test  in  the  same  way  as 
you  have  with  sphalerite,  i.  e.,  heat  a  fragment  or  some 
powder  of  the  mineral  strongly  on  charcoal,  in  the  O. 
F;  moisten  it  or  its  sublimate  with  a  drop  of  the  cobalt 
solution,  and  then  heat  again. 

Zinc  ox^de  then  becomes  yellowish-green. 

Tin  oxide  becomes  bluish-green. 

Magnesium  oxide,  magnesia,  becomes  pink. 

Aluminium  oxide,  alumina,  becomes  blue.  Try 
kaolinite. 

Silicon  oxide,  silica,  becomes  faint  blue.     Try  quartz. 

Strontium  oxide,  strontia,  becomes  gray.  Try 
celestite. 

Calcium  oxide,  lime,  becomes  gray.     Try  chalk. 

You  will  be  interested  to  note  in  this  connection  a 


236  THE   WORLD   OF  MATTER. 

few  characteristic  coatings  which  the  O.  F.  will  produce 
on  charcoal  without  the  assistance  of  any  reagent. 
White,  very  volatile,  gray  fumes,  indicate  arsenic 
white  near  the  assay,  blue  farther  off,  dense  white 
fumes  indicate  antimony. 

Purplish-brown,  indicates  silver.  In  lead  rich  in 
silver  the  color  may  be  brighter  red,  or  the  brow*i  may 
appear  in  spots  and  streaks  amid  the  yellow  oxide  cf 
lead. 

Lemon-yellow  while  hot,  sulphur  yellow  when  cold, 
white  and  bluish-white  at  a  distance,  volatile,  indi- 
cates lead. 

Always  wait  until  the  coating  is  completely  cool  be- 
fore judging  its  color. 

Do  not  mistake  the  white  ash  of  the  charcoal  for  a 
sublimate.  Sometimes  it  is  necessary  to  fuse  the  assay 
with  soda  in  order  to  get  the  sublimate. 

Do   not   fail    to   notice   the   odor   given    off  during"" 
heating. 

ROASTING. 

Substances  containing  sulphides  or  arsenides  must  be 
roasted  before  they  can  be  treated  with  soda  or  any 
other  flux.  Grind  small  fragments  of  iron  pyrites  to 
fine  powder.  Moisten  the  powder  and  transfer  to  a 
shallow  cavity  in  the  charcoal.  Heat  very  gently  at 
first  to  prevent  the  powder  from  melting  or  flying 
away.  After  some  of  the  sulphur  has  been  driven  off 
use  a  stronger  blast — the  O.  F.  and  the  R.  F.  alter- 
nately. 


feLOW-PIPE  ANALYSIS.  237 

Continue  as  long  as  there  is  the  slightest  smell  of 
sulphur,  no  matter  how  long  it  may  take.  Turn  the 
assay  on  the  other  side  and  treat  as  before.  Again  pul- 
verize the  assay  in  a  mortar.  The  powder  is  no  longer 
greenish,  but  red  like  that  of  hematite.  It  is  indeed, 
now,  an  oxide  of  iron.  As  some  sulphur  probably  re- 
mains, roast  it  again  on  both  sides.  Test  the  powder 
with  a  magnet  and  carefully  preserve  it  for  the  follow- 
ing experiments. 

TESTING    WITH    FLUXES. 

Heat  your  platinum  loop  and  dip  it  into  powdered 
borax.  Hold  it  over  the  flame  of  the  lamp  or  gas  and 
watch  the  melting  of 'the  borax  after  "intumescence;" 
but  to  prevent  particles  of  the  borax  from  flying  away, 
hold  it  in  the  flame. 

Add  more  borax  until  the  loop  is  filled.  Then  direct 
the  O.  F.  upon  it  with  the  blow-pipe,  until  it  becomes 
a  transparent  glass,  free  from  bubbles.  This  is  a  borax 
"bead."  Place  a  very  little  of  your  roasted  assay  upon 
the  bead.  If  it  will  not  stay,  smoke  the  bead  a  little 
over  the  flame,  or  heat  it  again  with  the  blow-pipe,  and 
flatten  it  gently  between  the  forceps  or  on  an  anvil.  Heat 
the  bead  over  the  lamp-flame;  just  enough  to  cause  the 
powder  to  stick  to  it.  Now  hold  the  loop  in  the  O.  F., 
beyond  the  point  of  the  blue  flame,  as  shown  in  Fig. 
30.  The  powder  begins  to  whirl  about  in  the  melting 
glass,  but  it,  too,  soon  dissolves,  and  the  glass  becomes 
clear  and  smooth. 

Hold  it  between  your  eye  and  a  window;  it  is  yellow, 


238  THE   WORLD   OF   MATTER. 

but  becomes  colorless  as  it  cools.  Add  a  little  more  of 
the  powder.  Dissolve  as  before  in  the  O.  F.  This 
time  it  appears  red  while  hot,  and  yellow  when  cold. 
Heat  it  now  in  the  R.  F.,  holding  it  farther  in  the 
flame  than  shown  in  Fig.  31,  as  your  loop  is  larger. 
The  bead  assumes  a  gree-nish  tint.  Add  still  more 
powder.  The  bead  becomes  brown  or  reddish  yellow 
in  the  O.  F.,  and  in  the  R.  F.  should  assume  the  pecu- 
liar bottle-green  of  junk-bottles. 

A  bead  which  contains  as  much  of  any  assay  as  it 
can  dissolve  is  said  to  be  saturated.  After  a  bead  is 
saturated,  you  may  again  dilute  it.  Melt  the  bead  and 
fling  it  into  a  clean  cup  or  mortar,  by  striking  the 
hand  which  holds  the  platinum  loop,  on  the  table.  Part 
of  the  assay  will  still  adhere  to  the  loop;  add  to  thi. 
enough  borax  to  make  a  new  bead.  This  will  resemble 
the  second  one  you  made.  Strike  this  off,  too;  dilute 
again  with  borax,  and  you  will  have  again  a  yellow 
bead  that  becomes  colorless  as  it  cools. 

Place  on  charcoal  a  piece  of  tinfoil,  and  on  this  lay 
the  two  beads  that  were  shaken  off.  Expose  the  beads 
and  the  foil  under  them  to  the  R.  F. ;  the  bead  should 
become  decidedly  green,  although  in  order  to  see  the 
color  you  may  have  to  pinch  the  bead,  which  clings  to 
the  coal,  upward  with  the  forceps  so  that"  you  can  look 
through  it. 

Care  of  the  platinum  wires*  The  test  being  finished, 
remove  the  bead  by  gentle  taps  with  a  hammer,  remove 
all  clinging  particles,  and  keep  the  wire  in  a  bottle  con- 

*Keep  several  platinum  loops  on  hand. 


BLOW-PIPE  ANALYSIS.  239 

taining  enough  diluted  sulphuric  acid  to  cover  the  loop. 
Before  using  again  rinse  in  water.  If  the  new  bead  of 
borax  is  not  perfectly  clear  and  colorless  both  when 
cold  and  after  heating,  throw  it  off  and  make  a  new 
one.  If  after  several  trials  the  color  still  persists,  make 
a  bead  with  soda,  shake  it  off,  and  put  the  loop  into  the 
acid  bottle  for  a  day.  Should  you  find,  while  testing  a 
mineral  in  the  borax  bead,  that  a  metallic  globule  is 
formed,  shake  the  bead  off  immediately  and  transfer  it 
to  charcoal. 

Test  other  specimens  of  iron  ores  in  the  borax  bead. 
The  oxides  and  carbonate  need  no  roasting. 

Try  a  little  powdered  chalk  in  the  bead.  It  effer- 
vesces as  it  dissolves  and  forms  a  colorless  glass.  Add 
a  small  fragment  instead  of  the  powder;  the  effect  is 
the  same.  Keep  on  adding  and  dissolving,  examining 
the  bead  each  time.  When  nearly  saturated  it  becomes 
translucent  instead  of  transparent  on  cooling,  and  as- 
sumes a  crystalline  structure.  Watch  it  with  a  magni- 
fying glass,  for  the  process  is  extremely  interesting. 
Add  a  little  more  chalk  and  the  bead  becomes  at  last 
almost  pure  white,  and  opaque.  If  you  direct  the  flame 
upon  the  bead  in  little  puffs  or  flashes  just  before  the 
point  of  saturation  is  reached  it  will  become  opaque 
even  in  the  flame.  This  is  called  faming  the  bead. 

Throw  off  part  of  the  assay,  dilute  the  rest  with  a 
little  borax  so  that  it  becomes  clear  again  and  try  the 
flaming.  It  is  chiefly  the  alkaline  earths  that  become 
thus  opaque  by  flaming. 

Compare  the  action  of  kaolin  with  that  of  chalk. 


240  THE   WORLD   OF   MATTER. 

Make  a  borax  bead  with  finely  powdered  quartz.  It, 
too,  dissolves  to  a  clear  glass,  but  more  slowly. 

From  these  experiments  we  learn  that  borax  causes 
even  the  most  refractory  metals  to  melt  in  the  heat  of 
the  blow-pipe. 

Substances  which  have  this  propeity  are  calledfluxes. 

The  following  are  the  principal  reactions  with  the 
borax  bead : 

Colorless. — The  alkaline  earths,  aluminum,  silica;  in 
O.  F.,  and  R.  F. 

Yellow  when  hot,  colorless  when  cold — in  O.  F., 
zinc,  cadmium,  lead,  bismuth.  In  R.  F.,  these  sub- 
stances become  gray  from  the  reduced  metal,  but  on 
further  heating  grow  clear  again. 

Milk-white — silver,  when  the  bead  is  saturated,  in  O. 
F.;  gray,  then  clear  in  R.  F. 

Yellow  in  O.  F. — iron,  titanium,  tungsten,  molybde- 
num, chromium  (greenish  yellow). 

Red  to  brown  in  O.  F. — hot;  iron,  uranium,  chromi- 
um:— cold;  nickel,  manganese. 

Red  in  R.  F., — copper,  when  the  bead  is  saturated  and 
cold ;  colorless  when  hot. 

Violet  in  O.  F., — nickel,  hot  (reddish- violet);  manga- 
nese, (deep  violet). 

Blue— cobalt,  O.  F.,  and  R.  F.;  copper,  O.  F.,  cold, 
greenish-blue. 

Green — copper,  OA  F.,  hot;  R.  F.,  bottle-green; 
chromium,  vanadium,  O.  F.  and  R.  F.,  cold;  uranium, 
R.  F.,  yellowish-green. 


BLOW-PIPE  ANALYSIS.  241 

EXAMINATION    WITH    SODA. 

Soda  beads  in  the  platinum  wire  are  not  often  used, 
but  it  is  worth  while  to  make  a  few.  The  bead  itsejf 
is  interesting.  After  it  has  become  well  fused,  notice 
how  it  begins  to  effervesce,  as  you  pass  it  from  the  O.  F. 
to  the  R.  F.,  also  that  it  is  transparent  while  hot,  and 
becomes  translucent  when  cool. 

Add  some  quartz  powder;  it  easily  dissolves,  with 
effervescence,  and  the  bead  on  withdrawal  from  the 
flame  loses  its  transparency.  Continue  adding  arid  dis- 
solving quartz,  and  presently  you  reach  a  point  where 
the  bead  remains  transparent  even  after  cooling. 

Try  orthoclase,  and  you  should  secure  the  same  re- 
sult. 

From  this  we  understand  that  silica  dissolves  readily 
and  with  effervescence  in  soda,  and  that,  if  the  propor- 
tion of  soda  is  not  too  great,  the  resulting  glass  will  be 
clear.  Indeed,  our  window-panes  and  common  glass- 
ware are  for  the  most  part  silicate  of  soda,  or  of  soda  and 
lime. 

In  most  cases  the  treatment  of  mineral  compounds 
with  soda  is  conducted  on  charcoal. 

Mix  some  powdered  quartz  with  about  three  times 
its  bulk  of  soda  and  transfer  the  paste  to  the  coal.  Treat 
it  with  O.  F.  for  a  considerable  time,  trying  to  collect 
the  mass  into  a  globule.  You  will  hardly  succeed. 
Probably  the  assay  will  spread  out  more  and  more,  and 
partly  sink  into  the  coal.  Now  make  another  mixture, 
taking  equal  parts  of  quartz  and  soda.  You  should 
succeed  without  much  trouble  in  forming  this  mixture 


242  THE   WORLD   OF 'MATTER. 

into  a  bead.  Continue  playing  the  O.  F.  upon  it,  caus- 
ing it  to  revolve  until  you  get  rid  of  nearly  all  bubbles. 
You  should  get  a  transparent,  nearly  colorless  bead. 

Next  try  a  small  splinter  of  orthoclase.  Place  it  in  a 
shallow  depression  in  the  charcoal  and  put  a  little  soda 
around  it.  Blow  gently,  as  you  always  should  at  the 
beginning.  See  the  soda  fuse,  and  begin  to  attack  the 
mineral;  effervescence  marks  the  beginning  of  the 
fusion;  the  edges  and  corners  are  first  dissolved.  Add 
a  little  more  soda  and  heat  again,  the  assay  spreads  out 
to  take  in  every  grain  of  the  salt,  and  then  rounds  up  to 
form  a  globule,  with  the  inner  part,  probably,  yet  undis- 
solved.  Other  additions  diminish  the  undissolved  part, 
and  the  bead  may  assume  a  dark  appearance  from  some 
impurities  taken  up.  Add  much  soda  and  the  mass  will 
spread  out.  It  takes  longer  to  do  this  work  than  to  de- 
scribe it,  but  the  experience  gained  during  the  faithful 
and  patient  performance  of  the  experiment  will  be 
worth  all  it  costs. 

You  should  still  have  some  of  the  powder  from  the 
roasted  pyrites.  Mix  all  that  is  left  with  about  three 
times  its  bulk  of  soda,  moisten,  and  transfer  to  the  char- 
coal. Give  it  a  long  and  strong  blast  with  the  R.  F., 
until  all  the  life  has  gone  out  of  the  mixture,  i.  e.  as  long 
as  you  can  observe  any  effect  from  the  heat,  and  even 
longer. 

Cut  out  the  black  mass  with  some  of  the  coal  under- 
neath it,  and  grind  it  to  a  powder  in  a  mortar,  adding  a 
little  water.  Set  the  mortar  with  its  contents  in  a  cup 
or  basin,  and  pour  water  in  the  vessel  until  it  covers  the 


BLOW-PIPE  ANALYSIS.  243 

mortar,  and  a  little  more.  The  lighter  portion  of  the 
assay  will  now  rise  from  the  mortar,  and  float  on  the 
water;  and  by  moving  the  mortar  about  under  the 
water  all  but  the  heaviest  sediment  can  be  floated  out. 

Now  remove  the  mortar,  pour-  the  water  from  it,  and 
carefully  transfer  the  sediment  to  a  piece  of  paper. 
When  dry,  examine  the  little  particles  with  a  magnify  - 
ing-glass.  Test  them  with  a  magnet.  It  is  a  good 
plan,  by  the  way,  to  fit  the  ends  of  your  magnet  with 
"stockings"  of  tissue  paper  reaching  half  way  up. 
Magnetic  substances  will  be  attracted  through  the 
paper,  and  they  will  drop  off  when  you  pull  the  magnet 
partly  out  of  the  stocking.  You  have  now  reduced 
the  oxide  to  metallic  iron. 

Powder  some  galenite,  mix  with  plenty  of  soda,  and 
treat  with  the  R.  F.  Let  the  globules  run  together, 
and  observe  the  action  of  the  large  globule  of  lead  as  it 
solidifies.  When  it  grows  cool  take  it  off  and  hammer 
it.  Observe  how  much  more  lead  you  get  in  this  way 
from  a  certain  quantity  of  galenite  than  by  reducing  the 
galena  without  soda. 

The  last  two  experiments  illustrate  the  use  of  soda  as 
a  flux  for  reducing  metals  from  their  compounds.  If 
any  metal  does  not  form  a  globule,  but  behaves  like 
iron,  forming  a  slag,  this  slag  must  be  treated  as  the 
iron  was,  that  is,  powdered  and  separated  by  the  float- 
ing process. 

If  then  the  metal  cannot  be  recognized  from  the 
sediment  in  the  mortar,  this  must  be  dissolved  in  a 
borax  bead,  that  its  nature  may  be  revealed  by  the  color 
imparted  to  the  bead. 


244  THE  WORLD   OF  MATTER. 

We  must  remember,  too,  that  the  treatment  with 
soda  on  charcoal  may  be  used  for  getting  a  coating  or 
sublimate  which  may  aid  in  determining  the  metal. 

All  reductions  on  coal  must  be  conducted  with  the 
R.F. 

If  you  suspect  that  the  dark  mass  or  hepar  resulting 
from  heating  a  metal  on  coal  with  soda  contains  sul- 
phur, crush  it  and  place  a  fragment  on  a  bright  silver 
coin,  adding  a  drop  of  water.  If  sulphur  is  present  it 
will  unite  with  the  silver  forming  silver  sulphide,  and 
leaving  a  brown  stain  on  the  coin.  Be  sure,  however, 
that  neither  your  soda  nor  your  fuel  contains  sulphur. 

Filtering  and  decanting.  To  separate  solutions 
from  an  undissolved  sediment,  or  from  a  precipitate, 
they  are  passed  through  filter-paper  placed  in  a  funnel ; 
or,  if  the  liquid  stands  clear  above  the  sediment,  may 
be  simply  poured  off,  or  decanted.  If  the  sediment  or 
precipitate  is  to  be  further  tested  it  should  be  washed 
either  by  pouring  water  over  it  as  it  lies  on  the  filter- 
paper,  and  letting  it  pass  through  until  all  acid  or  alkali 
is  removed,  or  by  repeated  shaking  up  and  decanting 
with  water. 


SUGGESTIONS  FOR  FURTHER  STUDY.         245 


CHAPTER  XVII. 

SUGGESTIONS    FOR    FURTHER    STUDY. 

No  experiments  have  been  described  in  this  book 
which  cannot  be  successfully  performed  without  assist- 
ance by  every  student,  no  matter  whether  he  has  had 
any  previous  training  or  not,  if  he  will  undertake  them 
resolutely  and  patiently,  and  in  the  order  given. 

Those  who  have  worked  their  way  with  us  to  this 
point  will  wish  to  continue  their  study  of  this  fascinat- 
ing science,  until  they  attain  the  power  of  recognizing 
at  sight,  or  of  determining  by  analysis,  every  specimen 
they  may  meet.  A  description  of  twenty-four  more 
common  minerals  is  therefore  added  for  practice.  It 
must  be  borne  in  mind,  however,  that  the  determina- 
tion of  the  names  of  minerals  is  by  no  means  the  chief 
aim  of  the  earnest  student.  It  is  rather  to  make  him- 
self thoroughly  acquainted  with  the  properties  of  min- 
erals, and  to  develop  and  strengthen  his  powers  of 
obserration  and  reasoning.  Carefully  to  observe,  and 
accurately  to  describe  your  specimens,  should  therefore 
be  your  main  object. 

It  is  almost  wholly  because  the  processes  required  to 
determine  minerals  necessarily  enforce  this  patient  and 
exact  personal  observation,  that  they  become  a  valuable 
means  of  education  and  training. 


246  THE   WORLD   OF  MATTER. 

You  will  do  well,  now,  to  procure  the  specimens 
whose  descriptions  follow. 

1.  Native  copper.     H-3;  lustre  and  streak,  metallic; 
color  red;  occurs  in  masses,  in   crystals,  and  in  beauti- 
fully branched  or  arborescent  forms,  sectile,  malleable, 
very  tough,  heavy. 

Comp. — Cu;  B.B.  fuses  to  a  globule,  try  tests  for  Cu. 

2.  Cinnabar.     H. 2-2.5;  lustre,  adamantine  to  dull; 
streak,  scarlet;  color,  red  to  dark  brown;  in  crystals,  or 
massive;  brittle;  very  heavy;  fracture  uneven. 

Comp.  HgS;  B.  B.  volatilizes;  Hg  and  S  reactions 
in  c.t.  with  and  without  soda.  Cinnabar  is  the  principal 
ore  of  mercury,  which  is  also  found  native. 

3.  Millerite,  (nickel  pyrites}.     H. 3- 3. 5;  lustre,  me- 
tallic; color,  bronze  yellow;  streak,  gray;  in  clusters  of 
fine  needle-shaped   crystals,  or  in  fibrous  crusts;  brittle; 
rather  heavy. 

Comp. — NiS;  B.  B.  on  charcoal  fuses  easily  to  a 
brittle,  magnetic  globule;  with  borax  bead  gives  Ni 
reaction;  roasted  and  fused  with  soda  on  charcoal  yields 
a  brittle  globule  of  nickel. 

4.  Pyrrhotite. — H.  about  4;  lustre,  metallic;  color, 
bronze  yellow,  tarnishing  to  copper  red;  streak,  gray, 
generally  massive;  brittle;  magnetic. 

Comp. — Fe7S8 ;  B.  B.  on  charcoal  fuses  to  a  magnetic 
globule;  yields  little  sulphur  in  c.  t. ;  softer  than  iron 
pyrites  and  harder  than  copper  pyrites;  magnetic. 

5.  Chalcopyrite    (copper  pyrites].     H.  3.5;   lustre, 
metallic;  color,  brass  yellow,  often  tarnished   to  deep 
yellow,  red,  blue,  etc.;  streak,  greenish  black;  crystal- 


SUGGESTIONS  FOR  FURTHER  STUDY.          247 

lized     or    massive;    fracture,    uneven;    brittle;    easily 
scratched  -with  a  knife. 

Comp. — CuFeS2;  B.B.  on  charcoal  fuses  easily  to 
a  magnetic  globule;  fused  with  soda  on  charcoal  yields 
a  globule  of  copper  and  iron.  Moisten  the  globule 
with  HC1.,  and  examine  the  flame  color  at  the  point  of 
the  O.  F.  Crush  the  globule  to  powder  and  dissolve  in 
a  few  drops  of  nitric  acid;  both  copper  and  iron  will  be 
dissolved.  Add  ammonia  until  the  iron  is  precipitated 
as  a  reddish  brown  powder;  the  liquid  will  then  be  blue. 
Also  roast  some  of  the  ore,  or  make  another  globule  of 
it  with  soda.  Pulverize,  and  saturate  a  borax  bead  with 
the  powder;  examine  the  bead  and  throw  it  off;  add 
more  borax  to  what  remains  on  the  wire,  examine  it 
both  hot  and  cold,  and  throw  off  again ;  repeat  this  un- 
til the  bead  becomes  almost  colorless,  and  make  a  record 
of  your  observations. 

6.  Ccrargy rite  (horn  silver). — H.   1.5;    lustre,  res- 
inous;   streak,    shining;     color,   pearl- gray,   brownish 
when  weathered ;  in  very  small  cubical  crystals  or  mass- 
ive; fracture  uneven;  easily  cut  with  a  knife. 

Comp. — AgCl;  melts  in  the  candle-flame.  B.  B.  on 
charcoal  with  O.  F.  yields  little  globules  of  silver. 
Better,  however,  fuse  on  charcoal  with  soda  in  R.  F., 
and  collect  all  the  silver  into  one  globule.  Observe  the 
coating  on  the  coal,  which  may  show,  besides  the  char- 
acteristic purple  brown  of  silver,  a  yellow  sublimate, 
indicating  the  presence  of  lead. 

7.  Zincite. — H.    4-4.5;     lustre,     brilliant;     streak, 
orange  yellow;  color,  bright  red;  generally   in  granu- 


248  THE  WORLD  OF  MATTER. 

lated   or   foliated   masses;    cleavage,   perfect;     brittle; 
rather  heavy. 

Comp. — ZnO.  B.  B.  infusible;  turns  black,  but  after 
cooling  turns  red  again.  On  charcoal,  with  and  without 
soda,  gives  zinc  coating. 

8.  Menaccanite  (titanic  iron). — H.5-6;  lustre,  met- 
allic  or   sub-metallic;    color,   black;   streak,  black;  in 
grains,  plates,  sometimes  large  tabular  crystals;  cleavage, 
distinct;  rather  heavy;  magnetic. 

Comp.— (Ti  Fe)2O3;  B.  B.  infusible;  fused  with 
soda  on  charcoal,  and  dissolved  in  HC1,  gives  Ti  re- 
action. 

9.  frranklinite. — H.  about  6;  lustre,  metallic;  color, 
iron  black;  streak,  reddish  brown  to  black;    massive  c/ 
in   crystals;    cleavage,    indistinct;    brittle;     fragments 
slightly  magnetic. 

Comp — (FeZnMn)2O4;  B.  B.  infusible;  with  ?sc/u3 
on  charcoal,  white  zinc  coating,  turning  green  if  treatec 
with  cobalt  solution.  In  soda  bead  assumes  a  green  co- 
lor in  O.  F.  Both  reactions  are  more  distinct  if  a  little 
borax  is  added  to  the  soda. 

10.  Ckromite. — H.  5-5;  lustre,  metallic,  or  sub- 
metallic;  streak,  brown;  color,  iron  black;  generally 
massive;  breaks  with  even  but  rough  surfaces;  not 
magnetic,  unless  in  very  small  particles. 

Comp. — FeCr2O4;  B.  B.  infusible;  with  borax 
bead  Cr  reaction. 

ii.  Cassiterite. — H.  6-7;  lustre,  splendent,  sub- 
metallic,  dull  on  exposed  surfaces;  streak,  brownish  to 
gray ;  color  commonly  brown  to  black ;  in  crystals ;  of- 


SUGGESTIONS  FOR  FURTHER  STUDY.          249 

ten  bean-shapea,  fibrous,  a^so  massive    and   compact; 
fracture  uneven;  brittle;  heavy. 

Comp. — SnO2 ;  B.  B.  infusible,  with  soda  on  char- 
coal yields  tiny  globules  of  tin.  See  Sn,  p. — The  prin- 
cipal ore  used  in  the  manufacture  of  tin. 

1 2.  Pyrolusite*  (black  oxide  or  dioxide  of  manganese) 
— H.  1-2.  5;  lustre,  metallic  to  earthy;  streak  and  color; 
black;  soils  the  fingers;  generally  massive,  columnar, 
radiated;  brittle,  rather  heavy. 

Comp. — MnO2;  B.  B.  infusible;  very  little  imparts 
an  amethyst  color  to  the  borax  bead.  Dissolve  in  HC1, 
heating  the  solution  slightly,  and  observe  the  odor  of 
chlorine. 

13.  Bcauxite. — H.  about  3;   lustre,    earthy;  color, 
white,  red   to  brown;  streak,  white   to  red;  composed 
of  small   round  concretions  like  little  peas,  (pisolitic), 
imbedded  in  a  compact  matrix;  fracture,  uneven,  brittle. 

Comp.—  Al2Fe2  O3+2H2O;  B.  B.  infusible;  de- 
crepitates strongly ;  in  c.  t.,  yields  water.  Try  reaction 
for  alumina;  for  iron. 

14.  Spodumene. — H.  6.5-7;    lustre,  pearly;    color, 
grayish  to   greenish  white;  streak,  white;  massive,  also 
often  in  large  crystals;  cleavage  perfect;  brittle. 

Comp. — Li6Al8Si15O45  ;  B.  B.  fuses  easily  with  in- 
tumescence, first  to  a  white  mass,  then  to  a  clear  glass, 
showing,  at  least  for  a  few  moments  during  the  treat  ^ 
ment  with  O.  F.,  the  lithia  reaction.  Try  the  tests  foi 
alumina  and  silica. 

15.  Willemitc. — H.  5.5;  lustre  vitreous  to  resinous^ 
color,  brown,  red,  yellow,  green,  also  colorless;  streak^ 


250  THE  WORLD  OF  MATTER. 

white;  translucent,  seldom  transparent;  generally 
compact,  fine  grained,  sometimes  in  small  crystals;  frac- 
ture uneven. 

Comp. — Zn3SiO4;  B.  B.  fuses  with  difficulty  and 
turns  white;  no  water  in  c.  t.;  with  HC1  gelatinizes 
perfectly;  an  important  ore  of  zinc.  » 

16.  Cinnamon  garnet,  (massive). — H.  about  7;  lus- 
tre, vitreous  to  resinous;  color,  commonly  red  or  brown, 
but  also  of  almost  every  other  color;  generally  in  crys- 
tals; also  massive;  brittle;  fracture  uneven. 

Comp. — Ca3Al2Si3O12;  B.  B.  fuses  less  easily  than 
vesuvianite  (the  next  specimen),  and  without  swelling, 
to  a  dark  glass. 

17.  Vesuvianite  (idocrase).     H.  6.5;  lustre,  vitreous 
to  resinous;  color,  brown  to  green;  streak,  white;  sub- 
transparent  to  nearly  opaque;  in  prismatic  crystals,  also 
massive;  fracture  uneven,  brittle. 

Comp.— (CaMg)8(AlFe)4Si7O28;  B.  B.  fuses  with 
swelling  to  a  dark  greenish  or  brownish  glass,  which 
shows  alkaline  reaction.  Fuse  a  few  fragments  thor- 
oughly on  charcoal  and  dissolve  in  HC1;  boil  it  well 
down  and  notice  the  gelatinizing  of  the  mineral. 

1 8.  Scapolite,  (ivernerite).     H.  5-6;  lustre,  vitreous 
to  pearly ;  color,  usually  light  gray,  blue,  lilac,  green, 
or  pink;. streak,  white;  transparent  to  nearly   opaque; 
crystallized  or  massive;  often  with  a  fibrous  or  colum- 
nar appearance ;  fracture,  inclining  to  conchoidal ;  brit- 
tle.^ 

Comp. — CaAl2Si2O8;  B.  B.  fuses  rather  easily,  and 
with  intumescence  to  a  whitish,  bubbly  glass,  which 
cannot  be  further  fused;  alkaline  reaction. 


SUGGESTIONS  FOR  FURTHER  STUDY.         251 

19.  Elccolite  (variety  ofmephelite,  H.  nearly  6; 
lustre,  vitreous  to  greasy;  color,  grayish;  streak,  white; 
translucent;  massive  or  in  large  crystals;  fibrous  ap- 
pearance on  broken  surfaces;  brittle. 

Comp.— (NaK)3Al2Si2O8  (Dana)  B.B.  fuses  quietly, 
but  not  easily,  to  a  white  glass  resembling  that  of  scapo- 
lite.  Gelatinizes  with  HC1  without  previous  fusion.  No 
alkaline  reaction. 

20.  Sphene  (titanite).     11.5-5.5;  lustre,  vitreous  to 
resinous,  color,  brown  to  black,  sometimes  yellow  or 
green;  streak  whitish;  transparent  to  opaque;  generally 
in  oblique,  thin-edged  crystals,  sometimes  massive ;  cleav- 
age often  perfect  in  one  direction,  giving  the  crystals  a 
laminated  appearance;  brittle. 

Comp. —  CaTiSiOgj  fuses  with  intumescence  to  a 
blackish  mass.  Try  test  for  Ti. 

21.  Calamine., — H.  4.5-5;  lustre,  vitreous  to  pearly; 
color,  various,  commonly  light  brown;  streak,  whitish; 
transparent  to  translucent;   massive,  or  forming  botry- 
oidal,    stalactitic,    or  radiated   incrustations    lined    with 
crystals  (generally  in  fissures  of  rock) ;  cleavage,  perfect 
in  crystalline  varieties;    fracture,   uneven  to  rough   in 
granular  or  earthy  varieties;  brittle. 

Comp.— Zn2Si  O4  +  H2O;  B.  B.  fuses  with  difficul- 
ty, turning  white.  In  c.  t.  yields  water.  With  soda  on 
charcoal  gives  zinc  coating;  treated  with  cobalt  solution 
green,  assay  blue.  Dissolves  in  HC1,  leaving  white 
residue.  Gelatinizes  on  boiling  down  the  acid.  An  im- 
portant ore  of  zinc. 

22.  Strontianite. — H.  3.5-4;  lustre,  vitreous;  color, 


252  THE   WORLD   OF   MATTER. 

white  to  yellowish  and  greenish;  streak,  white;  gener- 
ally massive,  fibrous  in  parallel  or  radiated  lines,  also 
globular;  transparent  to  translucent;  fracture,  uneven; 
brittle. 

Comp. — SrCO3 ;  B.  B.  fuses  with  difficulty,  white 
sprouts  appearing  on  the  points  and  edges ;  colors  the 
flame  crimson;  heated,  shows  alkaline  reaction.  Try 
reaction  for  carbon  dioxide.  Strontianite  is  used  in  the 
manufacture  of  fireworks. 

23.  Malachite  {green  copper  carbonate]. — H.  3.  5-4; 
lustre,  silky  to  earthy;  streak,  pale  green;  color,  green; 
generally  opaque,   sometimes  translucent;    massive   or 
forming  incrustations  which    may   be    mere   films,    or 
thicker  botryoidal,  stalactitic,  or  spongy  masses  of  com- 
pact and  fibrous  structure;  fracture,  uneven;  brittle. 

Comp.— Cu3CO4  +  H2O;  B.  B.  easily  fusible  to  a 
black  globule;  observe  the  green  flame  beyond  the 
globule.  Moisten  with  HC1  and  notice  the  flame. 
On  charcoal  fuses  to  a  globule  of  copper;  if  there  is 
difficulty,  add  a  little  soda,  running  it  into  a  bead  with 
the  O.  F.,  and  then  reducing  it  in  the  R.  F.  Try  other 
reactions  for  copper. 

24.  Azurite  (blue  copper  carbonate]. — H.  4;  lustre, 
vitreous  or  dull;  color  and  streak,  blue;  translucent  to 
opaque;  in  crystals,  or  massive,   also  compact,  earthy; 
brittle;  much  like  malachite  except  in  color. 

Comp. — Cu3C2O7  +  H3O;  behavior  with  reagents 
like  malachite.  Both  minerals  are  valuable  ores  of  cop- 
per. Malachite  is  often  worked  into  mantels,  table- 
tops,  and  various  ornaments. 


SUGGESTIONS  FOR  FURTHER  STUDY.         253 

REFERENCE  LIST 

of  the  principal  elements  in  minerals  and  their  charac* 
teristic  reactions. 

Ag. — Silver.  B.  B.  Heated  on  charcoal  in  O.  F. 
forms  a  reddish  brown  coating.  Dissolved  in  nitric 
acid  forms  a  whitish  cloud  (precipitate  of  Ag  Cl)  which 
settles  and  turns  dark  on  exposure  to  light,  and  which 
may  be  dissolved  again  by  the  addition  of  ammonia. 
Most  silver  ores  heated  on  charcoal,  alone  or  with  soda, 
yield  a  silver  globule. 

Al. — Aluminium.  (A12O3,  alumina)  B.  B.  A  frag- 
ment strongly  heated  on  charcoal,  or  in  the  forceps,  then 
moistened  with  cobalt  solution  and  heated  again,  as- 
sumes a  beautiful  blue  color. — All  color  reactions  should 
be  examined  by  daylight. — Sometimes  it  is  necessary  to 
pulverize  before  heating.  In  dark-colored  specimens 
the  blue  does  not  always  appear  distinctly;  if  these  are 
soluble  in  acids,  and  ammonia  be  added  to  the  acid  solu- 
tion, the  alumina  will  be  precipitated,  and  after  drying 
can  be  tested  with  the  cobalt  solution. 

As — Arsenic.  B.  B.  garlic  odor,  gray  fumes,  gray 
coating  on  charcoal,  distant  from  the  assay  and  easily 
driven  away  by  the  flame.  In  o.  t.  yields  a  white  crys- 
talline sublimate;  in  c.  t.  a  black  brilliant  sublimate. 

Au — Gold.  Imparts  no  characteristic  color  to  flame 
or  flux.  If  native  is  easily  recognized  by  its  color, 
malleabilty,  and  insolubility  in  any  one  of  the  acids. 

Ba — Barium.  (BaO,  baryta)  B.  B.  yellowish-green 
flame,  shown  by  all  minerals  containing  barium  except 
silicates.  If  soluble  in  HC1,  an  addition  of  H2SO4 
causes  a  heavy  white  precipitate.  BaSO4. 


&54  THE  WORLD   OF   MATTER. 

J3i — Bismuth.  B.  B.  on  charcoal  alone  or  with 
soda,  gives  a  characteristic  orange-yellow  sublimate. 
Treated  with  equal  parts  of  potassium  iodide  and  sulphur^ 
a  beautiful  red  precipitate  of  bismuth  iodide  is  formed. 

Bo — Boron.  B.  B.  Intense  yellowish-green  flame, 
especially  if  moistened  with  H2SO4. 

C — Carbon.  (CO2,  carbonic  acid,  or  anhydride)  Is 
set  free,  when  present  in  minerals,  by  HC1  and  all  the 
stronger  acids  causing  effervescence.  Sometimes  the 
mineral  must  be  pulverized,  and  sometimes  the  solution 
must  be  heated. 

CA— Calcium.  (CaO,  lime),  B.  B.  yellowish-red 
flame.  Many  minerals  containing  lime  give  an  alkaline 
reaction  after  being  highly  heated. 

Cl — Chlorine.  B.  B.  Prepare  a  bead  with  the  salt 
of  phosphorus,  (a  phosphate  of  sodium  and  ammonium), 
saturate  it  with  copper  oxide,  and  add  some  of  the 
powdered  mineral;  if  Cl  is  present  the  blow-pipe  flame 
will  be  colored  for  a  moment  intensely  blue.  (Try 
halite,  specimen  No.  28). 

Co — Cobalt.  B.  B.  imparts  to  the  borax  bead  a 
beautiful  blue  color.  Try  also  with  cobalt  solution. 

Cr — Chromium.  B.  B.  imparts  an  emerald-green 
color  to  the  borax  bead,  (cold)  in  both  O.  F.  and  R.  F. 

Cu — Copper.  B.  B.  green  flame;  blue  if  moistened 
with  HC1,  borax  bead,  O.  F.,  green,  R.  F.,  red,  ii 
highly  saturated.  Add  a  grain  of  salt  (NaCl),  and  ob- 
serve the  flame.  Most  copper  ores  are  reduced  to  me- 
tallic copper  when  fused  with  soda  on  charcoal. 

F — Fluorine.     If  the  powdered  mineral  be  laid  on, 


SUGGESTIONS  FOR  FURTHER  STUDY.         255 

glass,  moistened  with  one  or  two  drops  of  H  2  SO4 ,  and  set 
aside  for  a  day,  the  glass  will  be  etched.  This  corroding 
action  will  be  more  pronounced  if  the  powdered  min- 
eral containing  F  is  mixed  with  bisulphate  of  potas- 
sium, and  heated  in  the  c.  t. ;  a  strip  of  Brazil-wood 
paper  inserted  in  the  mouth  of  the  tube  will  turn  itraw- 
color. 

Fe — Iron.  B.  B.  besides  the  tests  already  given  on  p. 
204,  try  the  following:  Powder  some  of  the  mineral, 
add  dilute  HC1,  and  heat ;  let  the  sediment  settle,  and  de- 
cant the  clear  solution;  dilute  this  with  more  water; 
add  a  drop  of  a  solution  of  yellow  prussiate  of  potash 
If  iron  is  present,  the  solution  will  soon  turn  blue. 
(  Prussian  blue.) 

Hg — Mercziry.  Its  compounds  yield  a  metallic 
coating  when  heated  with  soda  in  the  c.  t.  The 
globules  of  mercury  are  sometimes  so  small  that  the 
coating  appears  white.  Use  the  magnifying-glass,  or 
brush  the  tiny  globules  together  with  a  strip  of  paper. 
Sulphide  of  mercury  yields  a  black,  volatile  sublimate, 
red  when  rubbed. 

K — Potassium.  B.  B.  is  often  recognized  by  the 
violet  color  it  imparts  to  the  flame.  If  sodium  is  pres- 
ent this  color  does  not  appear. 

LI — Lithium.  B.  B.  purplish  to  carmine  flame,  as 
in  lepidolite. 

Mg — Magnesium.  (Mg  O,  magnesia).  B.  B.  gen- 
erally indicated  by  the  pink  color  which  its  compounds 
assume  when  highly  heated,  and  treated  with  cobalt  so- 
lution. 


256  THfi   WORLD   OF   MATTER. 

Mil — Alanganese.  B.  B.  imparts  a  beautiful  ame- 
thyst color  to  the  borax  bead,  and  assumes  a  bright 
green  color  when  fused  with  soda. 

Na — Sodium.  B.  B.  colors  the  flame  intensely  red- 
dish yellow,  and  seems  to  make  it  larger. 

Nl — Nickel.  B.  B.  in  O.  F.  colors  the  borax  bead 
violet  when  hot,  reddish  brown  on  cooling;  in  R.  F. 
colorless  with  metallic  specks.  Nickel  ores  are  reduced 
to  a  magnetic  mass  on  charcoal. 

P — Phosphorus.  B.  B.  characteristic  green  flame, 
especially  when  moistened  with  H2SO4.  A  pulverized 
phosphate  fused  in  the  c.  t.  with  a  bit  of  metallic  mag- 
nesium or  sodium,  evolves  the  disagreeable  odor  of 
phosphoretted  hydrogen.  (Try  apatite.) 

Pb — Lead.  B.  B.  when  heated  with  soda  on  char- 
coal compounds  of  lead  yield  a  metallic  lead  globule;  a 
yellow  volatile  coating  appears  on  the  coal,  deeper  near 
the  assay,  and  shading  to  white  and  bluish. 

S — Sulphur.  B.  B.  on  charcoal  most  sulphides  are 
recognized  by  their  odor;  bisulphides,  as  FeS2,  by  the 
sublimate  of  S  in  the  tube.  Sulphides  dissolve  in 
HCM  with  effervescence  yielding  fumes  of  sulphuretted 
hydrogen — (rotten-egg  odor).  For  the  "hepar"  test  by 
which  the  presence  of  S  in  sulphates  can  be  detected, 
see  p.  — . 

$b — Antimony.  B.  B.  on  charcoal,  generally  recog- 
nized by  its  dense  white  fumes  and  white  sublimate. 
Same  in  o.  t.  Bluish  flame. 

Se — Selenium.  B.  B.  steel  gray,  volatile  sublimate; 
disagreeable  horse-radish  odor. 


SUGGESTIONS  FOR  FURTHER  STUDY.         257 

&i— Silicon.  [SiO2,  Silica]  B.  B.  heated  with  soda 
in  platinum  wire,  or  on  charcoal,  fuses  with  effervescence 
to  a  clear  glass ;  if  too  much  soda  is  used  a  slaggy  mass 
results. 

gn — Tin.  B.  B.  with  soda  on  charcoal  yields 
globules  of  metallic  tin,  often  so  minute  as  to  be  detected 
only  with  a  lens.  By  crushing  the  fused  mass  with  the 
adhering  coal  between  paper  and  heating  again,  adding  a 
little  soda,  the  globules  can  generally  be  collected  into  a 
larger  globule.  The  operation  requires  skill  and  care. 
Tin  yields  a  faint  yellow  sublimate, — not  volatile, — 
which  becomes  bluish  green  when  treated  with  the  co- 
balt solution. 

Sr — Strontium.  B.  B.  crimson  flame,  especially  if 
moistened  with  HC1. 

Ti — Titanium.  B.  B.  colors  a  bead  of  the  salt  of 
phosphorus  violet,  unless  too  much  iron  is  present.  In 
that  case  wrap  the  bead  in  a  small  piece  of  tinfoil,  trans- 
fer to  charcoal,  and  apply  the  R.  F.  The  iron  then 
will  unite  with  the  tin  in  a  metallic  globule,  leaving  the 
Ti  in  the  bead,  when  the  violet  color  will  appear. 

Tu — Tungsten.  Tungstic  acid  colors  the  salt  of 
phosphorus  bead  blue  in  R.  F.  If  iron  is  present  the 
bead  is  brownish  red ;  melting  on  charcoal  with  tinfoil 
or  zinc  the  bead  is  turned  blue. 

Zll — Zinc.  B.  B.  zinc  ores  on  charcoal  form  a  thick 
coating  of  zinc  oxide,  yellow  while  hot,  white  on  cool- 
ing. This,  if  treated  with  the  cobalt  solution  and  heated 
again,  changes  after  cooling  to  a  bright  yellowish  green. 

Zr — Zirconium.     Minerals  containing   zirconia,  dis- 


25&  THE   WORLD   OF  MATTER. 

solved  in  HC1  and  the  solution  diluted  with  water,  im- 
part an  orange-yellow  color  to  turmeric  paper. 

THE    USE    OF     THE   KEY. 

For  economy  of  space  the  properties  by  which  min- 
erals may  be  determined  are  usually  printed  in  a  key, 
or  in  tables.  To  illustrate  this,  a  short  key  to  the 
twenty-four  minerals  whose  descriptions  have  been 
given  on  pp.  202  to  225,  is  added.  Take  the  specimen 
of  beauxite  for  example. 

We  will  suppose  that  you  have  found  it,  and  do  not 
know  its  name.  Turn  to  the  key.  You  notice  that 
here  all  the  specimens  are  divided  into  two  classes.  I. 
Those  having  metallic  lustre.  II.  Those  whose  lus- 
tre is  non-metallic.  Your  specimen  falls  in  the  second 
class,  to  which  you  will  therefore  turn  at  once.  In  this 
class  you  observe  four  divisions,  A,  B,  C,  and  D,  based 
upon  the  color  of  the  streak.  As  your  specimen  has 
a  pink  streak  and  a  reddish  powder  it  must  be  referred 
to  division  B. 

In  this  division  you  find  three  minerals  distinguished 
by  their  action  under  the  blow-pipe ;  and  as  you  cannot 
melt  even  the  smallest  splinter  of  your  specimen,  al- 
though you  use  the  hottest  part  of  the  flame,  even  the 
magnifying-glass  revealing  no  trace  of  fusion  on  the 
thinnest  edges  or  sharpest  corners,  you  perceive  that  it 
must  be  either  zincite  or  beauxite. 

You  now  use  the  closed  tube  test.  Heating  some 
fragments  in  the  c.  t.,  you  observe  drops  of  water  form- 
ing in  the  upper  part  of  the  tube.  Therefore,  the 
specimen  must  be  beauxite. 


SUGGESTIONS  FOR  FURTHER  -STUDY.         259 

To  be  doubly  sure,  however,  you  will  turn  to  the 
reference  list,  page  253,  and  try  some  of  the  reactions 
for  aluminum  and  iron. 

Finally  you  will  turn  to  the  description  of  minerals 
— Number  13 — for  further  evidence  and  confirmation. 
Determine  all  the  specimens  named  in  the  key.  Even 
if  you  already  know  their  names,  it  will  give  you  ex- 
cellent practice,  and  prepare  you  to  use  the  larger 
tables  given  in  the  standard  books  of  reference. 

One  point  remains  to  be  noted:  You  will  not  al- 
ways get  in  practice  pure  specimens;  but  there  will 
often  be  a  mixture  of  several  minerals  in  one  specimen 
unless  you  have  the  crystal.  You  must  learn  at  once 
to  make  allowance  for  the  presence  of  impurities  in 
making  your  estimates  of  color,  hardness,  and  all  other 
physical  properties.  In  case  of  a  mixed  specimen,  it 
makes  little  difference  which  mineral  you  select  for 
analysis.  Give  the  preference,  as  a  rule,  to  the  one 
most  largely  and  plainly  developed;  also  in  general 
select  first  metallic  minerals.  Study  afterward  to  the 
best  of  your  ability  all  other  minerals  that  may  appear 
in  the  specimen,  always  remembering  that  the  chief 
benefit  to  you  will  come  from  the  acquisition  of  the 
power  and  habit  of  careful  and  accurate  observation, 
rather  than  from  the  mere  knowledge  of  names  which 
may  result  from  that  observation. 


26o  THE   WORLD   OF   MATTER. 


KEY      FOR       DETERMINING       TWENTY-FOUR       OF       THE 
MORE    COMMON    MINERALS. 

I.     LUSTRE     METALLIC. 

(Some  also  Sub-metallic). 

A. — COLOR   RED. 

No.   in 
Name.      Description. 

i .     Malleable ;  reaction  for  Cu Copper.  i 

B. — COLOR  YELLOW. 

(Sometimes  tarnished  on  exposed  surfaces  ) 

1.  Magnetic  before  fusion;  reaction  for  Fe,  Pyrrhotite.  4 

2.  Magnetic  after  fusion. 

a.  Reaction  for  Fe  and  Cu Chalcopyrite.       5 

b.  Reaction  for  Ni Millerite.  3 

C. — COLOR  GRAY  OR  BLACK, 
2.     Magnetic  before  fusion ;  reaction  for  Fe  with  borax  bead. 

a.  B.  B.  with  soda  on  charcoal,    white 

sublimate:    reaction  for  Zn Franklinite.         9 

b.  B.  B.  with  soda  on  charcoal,  no  subli- 
mate ;   reaction  for  Ti Menaccanite.      8 

2.  B.B.  magnetic  after  heating;  Cr  reaction  ;  Chromite.  10 

3.  B.  B.    not   magnetic:  infusible;  Mn  reac- 

action, Py  rolusite.          1 2 

II.    LUSTRE    NON-METALLIC. 

A. — STREAK  OR  POWDER  GRAY  TO  BROWN. 

1.  B.  B.  fuses  very  easily,  Ag  reaction, Cerargyrite.         6 

2.  B.  B.     infusible;    with  soda   on    charcoal 

yields  globules  of  Sn, "...  Cassiterite,        1 1 


SUGGESTIONS  FOR  FURTHER  STUDY.         261 

B. — STREAK  OR  POWDER  RED,  ORANGE  TO  PINK. 

1.  B.  B.    volatile;   in   c.   t.   black   sublimate 

and  Hg, Cinnabar. 

2.  B.  B.  infusible;   in  c.t.    black  while   hot; 

on  charcoal  Zn  reaction Zincite.  7 

3.  B.  B.  infusible;  water  in  c.t.;   Al  and  Fe 

reactions, Beauxite.  13 

C. — POWDER  GREEN  OR  BLUE. 

^    (  a.  Green, Malachite.          23 

Reaction  for  Cu  ]  ^  Blue>  » Azuritc  ^ 

D. — STREAK  WHITE  OR  VERY  LIGHT. 

B.  B.  fuses  easily,  and 

a.  Swells;      becomes    white;    opaque; 

colors  flame  purplish, Spodumene.  14 

b.  Swells  to  a  whitish  glass  full  of  bub- 
bles ;  alkaline  reaction, Scapolite  18 

c.  Shells  to  a  greenish  black  globule,.  .Vesuvianite.  17 

d.  Fuses  without  swelling  to  a  brownish 

or  greenish  glass, Garnet,  16 

2.  B.  B.  white  sprouts  on  surface;  crimson 

flame, Strontianite.      22 

3.  B.  B.  small  splinters  fuse 

a.  Quietly  to  a  white  glass ;  not  alkaline ; 

gelatinizes  with  HC1, Elaeolite.  19 

b.  With  intumescence    to    a    blackish 

mass ;    Ti  reaction, Sphene.  20 

4.  B.  B.   almost  infusible;    gelatinizes 

with  HC1;  Zn  reaction, 

a.  Yields  water  in  c.t Calamine.  21 

b.  Yields  no  water  in  c.  t Willemite.          15 

5.  infusible ;  does  not  gelatinize ;  yields  water 

in  c.t. ;  Al  reaction, Beauxite.  13 

If  you  are  now  desirous,  as  I  trust  you  are,  of  con- 


262 


THE  WORLD  OF  MATTER. 


tinuing  the  study  of  minerals,  you  will  need  a  book 
comprehensive  enough  to  enable  you  to  determine  by 
the  methods  you  have  learned  all  known  minerals  of 
any  importance.  It  gives  me  pleasure  in  closing  to 
recommend  Professor  W.  O.  Crosby's  Tables,  for  the 
Determination  of  Common  Minerals,  published  by  the 
author,  Boston,  ($1.00);  and  the  Manual  of  Determin- 
ative Mineralogy,  by  Prof.  George  G.  Brush,  John 
Wiley  &  Sons,  New  Tork,  [$3.50.] 

LIST    OF    SPECIMENS    PREPARED    TO    ACCOMPANY    THIS 
BOOK. 


1.  Talc. 

2.  Gypsum. 

3.  Calcite,    (crystal    of    calc 
sfar\ 

4.  Fluorite. 

5.  Apatite. 

6.  Orthoclase. 
7  Quartz. 

8.  Cryolite. 

9.  Corundum, 
10.  Limonite. 
n.  Hematite. 

12.  Magnetite. 

13.  Cuprite. 

14.  Cast  Zinc. 

15.  Carbon. 

16.  Sulphur. 

17.  Stibnite. 

18.  Prochlorite. 


19.  Quartz  crystal. 

20.  White  marble. 

21.  Sphalerite. 

22.  Celestite. 

23.  Ordinary  stratified  slate 

24.  Roofing-slate. 

25.  Kaolinite. 

26.  Muscovite. 

27.  Biotite. 

28.  Halite. 

29.  Iron  pyrites. 

30.  Galena. 

31.  Magnesium  wire. 

32.  Graphite. 

33.  Serpentine. 

34.  Hornblende.    (Amfhibole). 

35.  Labradorite, 

36.  Chrysotile. 


LIST  OF    PRINCIPAL    ELEMENTS. 

The  following  list  comprises  the  elements  found  in 


SUGGESTIONS  FOR  FURTHER  STUDY.         263 

the  minerals  referred  to  in  this  book.  The  principal  acid 
elements  are  printed  in  italics  ;  some  elements  as  arsenic, 
antimony,  and  manganese,  form  both  acids  and  bases. 
Oxygen  and  Hydrogen  unite  both  with  basic-elements 
and  acid-elements. 


Name.                  Symbol. 

Atomic 

Name.                   Symbol. 

Atomic 

Weights. 

Weights^ 

Aluminum 

Al 

273 

Chromium 

Cr 

52 

Antimony 

Cobalt 

Co 

59 

(Stibium) 

Sb 

122 

Copper 

Arsenic 

As 

75 

(Cuprum) 

Cu 

63-4 

Barium 

Ba 

i37 

Fluorine 

F 

19 

Beryllium 

Gold  (Aurum) 

Au 

I96 

(Glucinum 

Be 

(G)      9 

HYDROGEN 

H 

I 

Bismuth 

Bi 

208 

Iron  (Ferrum) 

Fe 

56 

Boron 

B 

ii 

Lead 

Bromine 

Br 

80 

(Plumbum) 

Pb 

207 

Calcium 

Ca 

4o 

LUi.tUm 

Li 

7 

\Jaruon 

C 

12 

Magnesium 

Mg 

24 

Chlorine 

Cl 

35-5 

Manganese 

Mn 

55 

Mercury  (Hy- 

Silicon 

Si 

28 

drargyrum) 

Hg 

200 

Sodium 

Molybdenum 

Mo 

96 

(Natrium) 

Na 

23 

Nickel 

Ni 

59 

Strontium 

Sr 

88 

Nitrogen 
OXYGEN 

N 
0 

H 
16 

Sulphur 

S 

32 

Phosphorus 

P 

3i 

Tin(Stannum) 

Sn 

118 

Platinum 

Pt 

197 

Tungsten 

Potassium 

(Wolfram) 

W 

184 

(Kalium) 

K 

39 

Vanadium 

V 

ci.4 

Selenium 

Se 

79 

O        T^ 

Silver 

Zinc 

Zn 

65 

(Argentum) 

Ag 

1  08 

Zirconium 

Zr 

90 

The  symbols  are  abbreviations  of  the  Latin  names  of 


264  THE  WORLD  OF  MATTER. 

the  elements;  the  atomic -weights  show  the  proportions, 
by  weight,  in  which  the  elements  combine.  For  in- 
stance: Galenite  is  lead  sulphide  PbS: 

The  atomic  weight  of  Pb  is       .       .    207 
"         "  «  S  is     .  32 

Together,.     .       .  \   .       ...       .    239 

Thus,  in  every  239  grains,  ounces,  or  pounds  of  ga- 
lenite  there  are  207  grains,  ounces,  or  pounds  of  lead, 
and  32  grains,  ounces,  or  pounds  of  sulphur. 


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